Coffee berry borer (Coleoptera: Scolytidae) population dynamics across Hawaii Island's diverse coffee-growing landscape: optimizing location-specific pesticide applications

A major challenge to area-wide management of coffee berry borer (Hypothenemus hampei Ferrari) (Coleoptera: Scolytidae) is understanding how a heterogeneous coffee-growing landscape affects coffee berry borer population dynamics across temporal and spatial scales. We examined coffee phenology, weather, coffee berry borer flight activity, infestation, coffee berry borer position within the fruit, and management across 14 commercial coffee farms from 2016 to 2018 on Hawaii Island to characterize variation among districts and elevations. Here we aim to determine whether the timing of pesticide applications might be optimized based on specific locations. We observed larger populations of coffee berry borer at low-elevation farms and in the Kona district compared to mid- and high-elevation farms and the Ka'u district. Temperature, relative humidity, and rainfall all differed significantly across districts and elevations. We also observed a trend of higher fruit production at low-elevation farms compared to high-elevation farms, and differences in the timing of fruit development. Infestation increased with higher pest pressure and air temperatures and reduced fruit availability early and late in the season. Lastly, the timing and number of management interventions varied among districts and elevations. Combining information on trap catch, infestation, coffee berry borer position, and plant phenology, we present an optimized pesticide spray schedule for each location and find that the number of sprays could be reduced by 33-75% in comparison to the existing integrated pest management recommendations while maintaining effective control. Implementing a coordinated area-wide approach refined by small-scale optimization will lead to improved management of coffee berry borer on individual farms and a reduction in pest pressure across the coffee-growing landscape.

Less is more: Fewer attract-and-kill sites improve the male annihilation technique against Bactrocera dorsalis (Diptera: Tephritidae)

The Male Annihilation Technique (also termed the Male Attraction Technique; "MAT") is often used to eradicate pestiferous tephritid fruit flies, such as Bactrocera dorsalis (Hendel). MAT involves the application of male-specific attractants combined with an insecticide in spots or stations across an area to reduce the male population to such a low level that suppression or eradication is achieved. Currently, implementations of MAT in California and Florida targeting B. dorsalis utilize the male attractant methyl eugenol (ME) accompanied with a toxicant, such as spinosad, mixed into a waxy, inert emulsion STATIC ME (termed here "SPLAT-MAT-ME"). While highly effective against ME-responding species, such applications are expensive owing largely to the high cost of the carrier matrix and labor for application. Until recently the accepted protocol called for the application of approximately 230 SPLAT-MAT-ME spots per km2; however, findings from Hawaii suggest a lower density may be more effective. The present study adopted the methods of that earlier work and estimated kill rates of released B. dorsalis under varying spot densities in areas of California and Florida that have had recent incursions of this invasive species. Specifically, we directly compared trap captures of sterilized marked B. dorsalis males released in different plots under three experimental SPLAT-MAT-ME densities (50, 110, and 230 per km2) in Huntington Beach, CA; Anaheim, CA; and Sarasota-Bradenton, FL. The plots with a density of 110 sites per km2 had a significantly higher recapture proportion than plots with 50 or 230 sites per km2. This result suggests that large amounts of male attractant may reduce the ability of males to locate the source of the odor, thus lowering kill rates and the effectiveness of eradication efforts. Eradication programs would directly benefit from reduced costs and improved eradication effectiveness by reducing the application density of SPLAT-MAT-ME.

Review of surveillance systems for tephritid fruit fly threats in Australia, New Zealand, and the United States

Many countries conduct fruit fly surveillance but, while there are guidelines, practices vary widely. This review of some countries in the Pacific region demonstrates the diversity of fruit fly surveillance practices. All utilize 3 parapheromones-trimedlure, cuelure, and methyl eugenol-to trap adult male fruit flies. Some target species are not attracted to these compounds so other attractants such as food-based lures are used in certain areas or circumstances. Lure loading and replacement cycles depend on the target species and the local climate. Malathion and dichlorvos (DDVP) are commonly used toxicants, but not in all countries, and other toxicants are being developed to replace these older-generation pesticides. Jackson and Lynfield are commonly used trap designs but newer designs such as cone and Biotrap are being adopted. Local factors such as chemical registrations and climate affect the choice of trap, lure, dispenser, toxicant, and bait concentration. These choices affect the efficacy of traps, in turn influencing optimal trap deployment in space and time. Most states now follow similar practices around trap inspection, servicing, and data handling, but these processes will be disrupted by emerging automated trap technologies. Ultimately, different practices can be attributed to the unique fruit fly risk profiles faced by each state, particularly the suite of fruit flies already present and those that threaten from nearby. Despite the diversity of approaches, international trade in fruit continues with the assurance that fruit fly surveillance practices evolve and improve according to each country's risk profile and incursion experience.

Previously introduced braconid parasitoids target recent olive fruit fly (Bactrocera oleae) invaders in Hawai'i

The olive fruit fly Bactrocera oleae (Diptera: Tephritidae) was detected on Maui and Hawai'i Islands in 2019, affecting yields and quality of the state's emerging olive oil industry. Given previous parasitoid releases to control other invasive frugivorous tephritids in Hawai'i, we were interested in determining whether these parasitoids were naturally targeting recent olive fly invaders in field, if local olive cultivar differences affected parasitization rates, and if there was a seasonal pattern of parasitization that could inform future management decisions. To address these questions, we collected data from olive growing in Hawai'i during 2021 and 2022. During the fruiting season we collected monthly samples and reared out B. oleae in the lab. We detected two previously introduced braconid wasps: first Diachasmimorpha tryoni during 2021 and 2022 and later Fopius arisanus during the 2022 collection. Cultivar effects were limited to a single site in our study, where more D. tryoni were reared from 'Arbequina' olives. Seasonality of olive fruit fly and parasitoid activity was earlier in lower elevation sites, as expected based on tree phenology and temperature-dependent insect development. This represents the first report of D. tryoni parasitism activity against B. oleae and may reflect elevational effects combined with the ecological complexity in interactions between multiple invasive arthropod pests, their invasive and cultivated plant hosts, and introduced braconid parasitoids.

Simulation to investigate site-based monitoring of pest insect species for trade

Pest insect surveillance using lures is widely used to support market access requirements for traded articles that are hosts or carriers of quarantine pests. Modeling has been used extensively to guide the design of surveillance to support pest free area claims but is less commonly applied to provide confidence in pest freedom or low pest prevalence within sites registered for trade. Site-based surveillance typically needs to detect pests that are already present in the site or that may be entering the site from surrounding areas. We assessed the ability of site-based surveillance strategies to detect pests originating from within or outside the registered site using a probabilistic trapping network simulation model with random-walk insect movement and biologically realistic parameters. For a given release size, time-dependent detection probability was primarily determined by trap density and lure attractiveness, whereas mean step size (daily dispersal) had limited effect. Results were robust to site shape and size. For pests already within the site, detection was most sensitive using regularly spaced traps. Perimeter traps performed best for detecting pests moving into the site, although the importance of trap arrangement decreased with time from release, and random trap placement performed relatively well compared to regularly spaced traps. High detection probabilities were achievable within 7 days using realistic values for lure attractiveness and trap density. These findings, together with the modeling approach, can guide the development of internationally agreed principles for designing site-based surveillance of lure-attractant pests that is calibrated against the risk of non-detection.

Transect-based trapping for area-wide delimitation of insects

Typical delimitation trapping survey designs for area-wide (nonlocalized) insect populations are regularly spaced grids, and alternative shapes have not been evaluated. We hypothesized that transect-based designs could give similar detection rates with significantly shorter servicing distances. We used the TrapGrid model to investigate novel "trap-sect" designs incorporating crossed, spoked, and parallel lines of traps, comparing them to a regular grid, in single survey and multiple-site scenarios. We calculated minimum servicing distances and simulated mean probabilities of detecting a pest population, judging overall performance of trap network designs using both metrics. For single sites, trap-sect designs reduced service distances by 65-89%, and most had similar detection probabilities as the regular grid. Kernel-smoothed intensity plots indicated that the best performing trap-sect designs distributed traps more fully across the area. With multiple sites (3 side by side), results depended on insect dispersal ability. All designs performed similarly in terms of detection for highly mobile insects, suggesting that designs minimizing service distances would be best for such pests. For less mobile pests the best trap-sect designs had 4-6 parallel lines, or 8 spokes, which reduced servicing distances by 33-50%. Comparisons of hypothetical trap-sect arrays to real program trap locations for 2 pests demonstrated that the novel designs reduced both trap numbers and service distances, with little differences in mean nearest trap distance to random pest locations. Trap-sect designs in delimitation surveys could reduce costs and increase program flexibility without harming the ability to detect populations.

Harmonic radar tracking of individual melon flies, Zeugodacus cucurbitae, in Hawaii: Determining movement parameters in cage and field settings

Tephritid fruit flies, such as the melon fly, Zeugodacus cucurbitae, are major horticultural pests worldwide and pose invasion risks due primarily to international trade. Determining movement parameters for fruit flies is critical to effective surveillance and control strategies, from setting quarantine boundaries after incursions to development of agent-based models for management. While mark-release-recapture, flight mills, and visual observations have been used to study tephritid movement, none of these techniques give a full picture of fruit fly movement in nature. Tracking tagged flies offers an alternative method which has the potential to observe individual fly movements in the field, mirroring studies conducted by ecologists on larger animals. In this study, harmonic radar (HR) tags were fabricated using superelastic nitinol wire which is light (tags weighed less than 1 mg), flexible, and does not tangle. Flight tests with wild melon flies showed no obvious adverse effects of HR tag attachment. Subsequent experiments successfully tracked HR tagged flies in large field cages, a papaya field, and open parkland. Unexpectedly, a majority of tagged flies showed strong flight directional biases with these biases varying between flies, similar to what has been observed in the migratory butterfly Pieris brassicae. In field cage experiments, 30 of the 36 flies observed (83%) showed directionally biased flights while similar biases were observed in roughly half the flies tracked in a papaya field. Turning angles from both cage and field experiments were non-random and indicate a strong bias toward continued “forward” movement. At least some of the observed direction bias can be explained by wind direction with a correlation observed between collective melon fly flight directions in field cage, papaya field, and open field experiments. However, individual mean flight directions coincided with the observed wind direction for only 9 out of the 25 flies in the cage experiment and half of the flies in the papaya field, suggesting wind is unlikely to be the only factor affecting flight direction. Individual flight distances (meters per flight) differed between the field cage, papaya field, and open field experiments with longer mean step-distances observed in the open field. Data on flight directionality and step-distances determined in this study might assist in the development of more effective control and better parametrize models of pest tephritid fruit fly movement.

Mating Competitiveness of Bactrocera dorsalis (Diptera: Tephritidae) Males From a Genetic Sexing Strain: Effects of Overflooding Ratio and Released Females

The oriental fruit fly, Bactrocera dorsalis (Hendel), is a global pest that infests a range of fruit and vegetables. Males are attracted to methyl eugenol, and control is often achieved by the Male Annihilation Technique, where methyl eugenol + insecticide dispensers are deployed to eliminate males, preclude matings, and reduce population growth. The Sterile Insect Technique (SIT) has also been used to control B. dorsalis. The SIT involves the release of mass-reared, sterilized males to achieve matings with wild females, who then produce inviable eggs. Two key elements of SIT include the overflooding ratio achieved (sterile: wild males) and the strain type utilized, namely bisexual or genetically sexed (allowing male-only releases). Here, we describe the effects of these two factors on the mating competitiveness of a males from a genetic sexing strain of B. dorsalis, termed DTWP. Mating success was scored for DTWP versus wild males in field cages at ratios of 1:2, 1:1, 2:1, and 10:1 both when DTWP females were or were not concurrently released with DTWP males. Close correspondence was found between observed numbers of matings of particular male-female combinations and expected numbers based on the numbers of flies released of each sex and each strain. As a result, the proportion of total matings achieved by the DTWP across the eight treatments showed a corresponding increase with overflooding ratio. At a given ratio, DTWP males had a higher relative mating success when DTWP females were absent rather than present, although the reason for this was unclear.

Identifying an Optimal Screen Mesh to Enable Augmentorium-Based Enhanced Biological Control of the Olive Fruit Fly Bactrocera oleae (Diptera: Tephritidae) and the Mediterranean Fruit Fly Ceratitis capitata (Diptera: Tephritidae)

The augmentorium is a cost-effective screened enclosure designed to receive fruits infested with insect pests, retain the pests inside but let their natural enemies escape to enhance biological control of pest populations. Screen selection is critical to ensure that an augmentorium is effective for a particular system. Here we tested five types of screens with a mini-augmentorium design and measured the escape of four insect species under laboratory conditions: the pests olive fruit fly Bactocera oleae (Rossi) (Diptera: Tephritidae) and Mediterranean fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), and the parasitoids Psyttalia lounsburyi (Silvestri) (Hymenoptera: Braconidae) and Psyttalia ponerophaga (Silvestri) (Hymenoptera: Braconidae). The sex ratio of insects that escaped the screens was compared to the sex ratio of insects that could not escape. Results showed that one screen type ('crystal mesh') was the best for the purpose of designing a functional augmentorium: it retained 90% of B. oleae adults and 100% of C. capitata adults while letting 72% of Psyttalia lounsburyi adults and 94% of P. ponerophaga adults escape. The other screen types tested were suboptimal, either because they let too many flies freely escape or because they retained too many parasitoids. Sex ratio was almost always similar for insects that managed to escape the screens and insects that were retained, except for P. ponerophaga and the screen type 'light mesh'. These results are promising for the development of a functional augmentorium against the olive fruit fly and further implementation against Mediterranean fruit fly.

Evaluating Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) Response to Methyl Eugenol: Comparison of Three Common Bioassay Methods

Insect responses to chemical attractants are often measured using olfactory bioassays prior to testing in field experiments. The attraction of sexually mature male Bactrocera dorsalis to methyl eugenol (ME) and the loss of attraction by ME pre-fed males have been demonstrated in laboratory bioassays and field trapping studies. It has been suggested that ME nonresponsiveness can be exploited to improve the effectiveness of B. dorsalis management programs by protecting sterile males from ME-based control measures. Currently, work is underway to identify alternatives that reduce or eliminate ME response. To support the development of compounds and evaluation of their effect on B. dorsalis attraction to ME, we compared the effectiveness of three common bioassay methods that have been used to measure lure response in Bactrocera flies under controlled conditions (choice assays using Y-tube [Y], small-cage arena [SC], and rotating carousel field-cage [RC]) to determine which bioassay method is efficient and reliable. A series of bioassays comparing ME-exposed and ME-naïve wild-type and genetic sexing strain males showed that the RC and SC were effective at both observing attraction to ME and detecting a significant reduction in ME response from ME-exposed males. However, the male attraction to ME and a significant decrease in response to ME after ME feeding was not observed in our Y-tube assays. These suggest that RC and SC are preferable options to evaluate ME non-responsiveness in B. dorsalis, and that Y-tube tests are difficult to administer correctly.

Influence of seasonal and climatic variables on coffee berry borer (Hypothenemus hampei Ferrari) flight activity in Hawaii

Coffee berry borer (CBB, Hypothenemus hampei Ferrari) is the most serious insect pest of coffee worldwide, yet little is known about the effect that weather variables have on CBB flight activity. We sampled flying female CBB adults bi-weekly over a three-year period using red funnel traps baited with an alcohol lure at 14 commercial coffee farms on Hawaii Island to characterize seasonal phenology and the relationship between flight activity and five weather variables. We captured almost 5 million scolytid beetles during the sampling period, with 81-93% of the trap catch comprised of CBB. Of the captured non-target beetles, the majority were tropical nut borer, black twig borer and a species of Cryphalus. Two major flight events were consistent across all three years: an initial emergence from January-April that coincided with early fruit development and a second flight during the harvest season from September-December. A generalized additive mixed model (GAMM) revealed that mean daily air temperature had a highly significant positive correlation with CBB flight; most flight events occurred between 20-26°C. Mean daily solar radiation also had a significant positive relationship with flight. Flight was positively correlated with maximum daily relative humidity at values below ~94%, and cumulative rainfall up to 100 mm; flight was also positively correlated with maximum daily wind speeds up to ~2.5 m/s, after which activity declined. Our findings provide important insight into CBB flight patterns across a highly variable landscape and can serve as a starting point for the development of flight prediction models.

Simulation-Based Investigation of the Performance of Delimiting Trapping Surveys for Insect Pests

Fully trapped survey designs are widely used to delimit adventive pests populations that can be detected using traps and lures. Delimitation includes verifying the presence of the pest and determining its spatial extent. The size and shape of the survey design and the density of traps can vary; however, resulting variation in detecting efficiency is often unknown. We used a trapping network simulation model with diffusion-based insect movement to investigate delimiting survey trapping design performance for fully trapped and some modified designs. Simulations included randomized outbreak locations in a core area and a duration of 30 d. We assessed impacts of insect dispersal ability, grid size and shape, and trap attractiveness and density on survey performance, measured as mean probability of capturing individual pests [p(capture)]. Most published grids are square, but circles performed equally well and are more efficient. Over different grid sizes, p(capture) increased for insects with greater dispersal ability but was generally unresponsive to size because most captures occurred in central areas. For low dispersing insects, the likelihood of egress was approximately zero with a 3.2-km square grid, whereas an 11.3-km grid was needed to contain highly vagile insects. Trap attractiveness affected p(capture) more strongly than density: lower densities of poorly attractive traps may underperform expectations. Variable density designs demonstrated potential for cost savings but highlighted that resource-intensive outer bands are critical to boundary determination. Results suggesting that many grids are oversized need empirical verification, whereas other principles, such as using circular shapes, are readily adoptable now.

Spinosad resistance in field populations of melon fly, Zeugodacus cucurbitae (Coquillett), in Hawaii

BACKGROUND

Control of Zeugodacus cucurbitae, a serious agricultural pest worldwide, often includes or is dependent on the use of spinosad-based insecticides. This is especially the case in Hawaii, where GF-120, a protein bait containing spinosad as the active ingredient, has been in use as a key integrated pest management (IPM) tool against this Tephritid for the last two decades. Here, we report on resistance to spinosad [resistance ratios (RRs) and median lethal concentration (LC₅₀ )] in Hawaii's populations of Z. cucurbitae.

RESULTS

High resistance was found in populations from three farms on Oahu (RR = 102-303; LC₅₀  = 191-567 mg L^-1 ) and in a population from Maui (RR = 8.50; LC₅₀  = 15.9 mg L^-1 ). These will be problematic for control given that the most concentrated dilution ratio on the GF-120 label is 96 mg L^-1 of spinosad (1 part GF-120 to 1.5 parts water). Background resistance in a naïve wild population from the Island of Hawaii (RR = 2.73; LC₅₀  = 5.1 mg L^-1 ) was relatively low compared with a spinosad-susceptible laboratory colony (LC₅₀  = 1.87 mg L^-1 ). Resistance in the three Oahu and one Maui populations declined over generations in the absence of spinosad but remained elevated in some cases. Moreover, melon flies collected from one of the Oahu farms 1 year after the cessation of spinosad use revealed high persistence of resistance.

CONCLUSION

Compared with a 2008 survey of spinosad resistance, our findings indicate a 34-fold increase in resistance on one of the Oahu farms over 9 years. The evolution and persistence of high levels of resistance to spinosad in Z. cucurbitae in Hawaii highlights the need for alternative control tactics, particularly rotation of active ingredients. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Mosquito sound communication: are male swarms loud enough to attract females?

Given the unsurpassed sound sensitivity of mosquitoes among arthropods and the sound source power required for long-range hearing, we investigated the distance over which female mosquitoes detect species-specific cues in the sound of station-keeping mating swarms. A common misunderstanding, that mosquitoes cannot hear at long range because their hearing organs are 'particle-velocity' receptors, has clouded the fact that particle velocity is an intrinsic component of sound whatever the distance to the sound source. We exposed free-flying Anopheles coluzzii females to pre-recorded sounds of male An. coluzzii and An. gambiae s.s. swarms over a range of natural sound levels. Sound levels tested were related to equivalent distances between the female and the swarm for a given number of males, enabling us to infer distances over which females might hear large male swarms. We show that females do not respond to swarm sound up to 48 dB sound pressure level (SPL) and that louder SPLs are not ecologically relevant for a swarm. Considering that swarms are the only mosquito sound source that would be loud enough to be heard at long range, we conclude that inter-mosquito acoustic communication is restricted to close-range pair interactions. We also showed that the sensitivity to sound in free-flying males is much enhanced compared to that of tethered ones.

Flight Burst Duration as an Indicator of Flight Ability and Physical Fitness in Two Species of Tephritid Fruit Flies

We introduce a method to quantify flight ability and physical fitness of individual fruit flies which we term 'Flight Burst Duration' (FBD). This consisted of tethering individual insects by the dorsal thorax using a vacuum and measuring the length of time the insect beats its wings while suspended off a surface. Consecutive measurements with Bactrocera dorsalis Hendel (Dipera: Tephritidae) and Zeugodacus cucurbitae Coquillett (Diptera: Tephritidae) in the same day and across days indicated that a single measurement was sufficient, and that FBD was consistent and repeatable. Insects under stress from starvation displayed shorter FBD over time, and we suggest that the measure also relates to the physical condition or survival fitness of the individual. Though somewhat laborious and time-consuming, we propose that FBD can be useful for research studies requiring individual-level phenome data and for obtaining estimates quality and dispersive movement for insects.

Evaluation of Exclusion Netting for Coffee Berry Borer (Hypothenemus Hampei) Management

Exclusion nets are increasingly being used to protect a variety of agricultural crops from insect pests as a sustainable alternative to chemical controls. We examined the efficacy of exclusion nets in controlling the world's most damaging insect pest of coffee, Hypothenemus hampei (coffee berry borer), on two small-scale coffee farms on Hawai'i Island. We recorded microclimate data, fruit infestation, population per fruit, sex ratio, mortality by Beauveria bassiana, coffee yield and quality in four paired exclusion and control (un-netted) plots on both farms. Mean and maximum daily temperature and relative humidity were similar between treatments, while mean and maximum daily solar radiation was reduced by ~50% in exclusion plots. Green and ripe fruit from exclusion plots had significantly lower infestation compared to un-netted control plots at both farms. We observed no significant difference between exclusion and control plots in the number of CBB per fruit or the female:male sex ratio. CBB mortality was significantly higher in control relative to exclusion plots in one of the two farms. Ripe fruits harvested from exclusion plots were on average significantly heavier and wider than those from control plots; however, there was no significant difference in the average yield per tree between treatments. Lastly, coffee quality was not significantly different between control and exclusion plots. Our results suggest that with complete sanitation prior to net installation in an environment where CBB is actively circulating, exclusion netting can successfully control CBB on small-scale coffee farms without reducing coffee yield or quality, and has the potential to lower production and labor costs by eliminating the need to spray pesticides.

Postharvest Population Reservoirs of Coffee Berry Borer (Coleoptera: Curculionidae) on Hawai'i Island

Coffee berry borer, Hypothenemus hampei Ferrari (Coleoptera: Curculionidae: Scolytinae), is the most damaging insect pest of coffee worldwide. Old coffee berries (raisins) are widely acknowledged as coffee berry borer reservoirs, yet few studies have attempted to quantify coffee berry borer populations in raisins remaining on farms postharvest. We collected ground and tree raisins at six coffee farms on Hawai'i Island to assess raisin density, infestation, coffee berry borer abundance, and adult mortality in three areas of each farm: trees, driplines (ground below the tree foliage), and center aisles (ground between tree rows). We also assessed infestation of the new season's crop by conducting whole-tree counts of infested green berries. Mean raisin density was significantly higher in the dripline compared to the center aisle and trees (131 vs 17 raisins per m2 and 12 raisins per tree, respectively). Raisin infestation was significantly higher in samples from trees (70%) relative to those from the dripline (22%) and center aisle (18%). Tree raisins had significantly higher coffee berry borer abundance compared to both areas of the ground (20 vs 3-5 coffee berry borer per raisin). Adult mortality was significantly higher on the ground (63-71%) compared to the trees (12%). We also observed a significant positive correlation between ground raisin density and infestation of the new season's crop. Across all farms, we estimated that 49.5% of the total coffee berry borer load was present in dripline raisins, 47.3% in tree raisins, and 3.2% in center aisle raisins. Our findings confirm the importance of whole-farm sanitation in coffee berry borer management by demonstrating the negative impact that poor postharvest control can have on the following season's crop.

Raspberry Ketone Trifluoroacetate Trapping of Zeugodacus cucurbitae (Diptera: Tephritidae)in Hawaii

Melon fly, Zeugodacus cucurbitae (Coquillett), is a serious pest of tropical horticulture, causing damage to cucurbits, other fruiting vegetables, and certain tree fruits. The deployment of male lures comprises an important component of several detection and control strategies for this pest, with the main male attractant currently in use being cuelure (CL). A novel fluorinated analog of CL, raspberry ketone trifluoroacetate (RKTA), has been developed for the control of Bactrocera tryoni, a related pest; here, we test this compound for attraction to Z. cucurbitae. In outdoor screen cage testing, observations showed both more flies on filter papers, and a higher percentage of flies feeding, on papers treated with RKTA than on those with CL or melolure (ML). Field trapping with both yellow sticky traps and bucket traps found that RKTA captured more flies during the first 6 h of trapping than CL, while trap captures in the subsequent 18 h did not differ between the two lures. When comparing combined 24 h trap captures, yellow sticky traps containing RKTA captured more flies than those with CL, while bucket trap captures did not vary by lure. Analysis of lures weathered on filter paper found that nearly all applied RKTA hydrolyzed to RK within 6 h. Fine-scale melon fly behaviors digitally recorded in the field showed median resting distances from the lure of responding flies were shorter for RKTA than for CL. This study demonstrates the inherent attractiveness of RKTA while also highlighting the instability of this compound due to hydrolysis.

Comparative Cold Tolerance in Ceratitis capitata and Zeugodacus cucurbitae (Diptera: Tephritidae)

Cold tolerance studies were conducted with the egg and larval stages of Mediterranean fruit fly, Ceratitis capitata (Wiedemann) and melon fly, Zeugodacus (Bactrocera) cucurbitae (Coquillett) in Navel oranges to determine whether quarantine cold treatments approved for C. capitata might also be effective against Z. cucurbitae. Navel orange is a good host for C. capitata and a poor host for Z. cucurbitae, and therefore, artificial infestation of fruit was used to facilitate comparisons. Laboratory-reared eggs and larvae were inserted in the center of Navel oranges, placed in cold storage chambers at 1.5-2.0°C for 1, 2, 4, 6, 8, 10, 12, or 14 d, then removed, and evaluated for egg hatch or larval survival. Time-response data were analyzed using linear mixed-effects models, probit analysis, and visual inspection of survivorship graphs. C. capitata eggs were significantly more cold tolerant than Z. cucurbitae eggs, and Z. cucurbitae larvae were generally more cold tolerant than C. capitata larvae. C. capitata eggs and Z. cucurbitae second instar larvae were the most cold-tolerant life stages, and they were not significantly different from each other. Results suggest that cold treatment at ≤1.5°C for a minimum of 14 d would be sufficient to achieve disinfestation of C. capitata and Z. cucurbitae. The inherent cold tolerance in Z. cucurbitae is equal to or higher than that of C. capitata, and therefore, cold treatment protocols developed for C. capitata may not always be effective against Z. cucurbitae.

Terminalia Larval Host Fruit Reduces the Response of Bactrocera dorsalis (Diptera: Tephritidae) Adults to the Male Lure Methyl Eugenol

Methyl eugenol (ME) is a powerful semiochemical attractant to males of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), and is the keystone of detection, control, and eradication programs against this polyphagous and highly invasive tephritid pest. Despite its status as a model lure against B. dorsalis, variation among individuals in their attraction is known, independent of the generally increasing attraction with age and decreases with previous exposure. Here we report that adult male B. dorsalis that fed on Terminalia catappa L. (Myrtales: Combretaceae) (tropical almond) fruit as larvae have a significantly lower behavioral response to ME compared with wild males from Psidium guajava L. (Myrtales: Myrtaceae) or colony-reared males raised on artificial larval diet. F1 males from the tropical almond stock reared on artificial larval diet did not show reduced attraction to ME, suggesting that the lowered response of parental males (sires) results from the host fruit itself, perhaps its relatively high amount of ME. Experiments with ME added to artificial diet lend some support to this interpretation. In addition to the results above, we report on quantities of ME in three different host fruits (T. catappa, P. guajava, and Carica papaya L. (Brassicales: Caricaceae)) of B. dorsalis. This study indicates the need for further research on the effect of host fruit on adult response to lures in economically important tephritids.

The Hawaii Protocol for Scientific Monitoring of Coffee Berry Borer: a Model for Coffee Agroecosystems Worldwide

Coffee berry borer (CBB) is the most devastating insect pest for coffee crops worldwide. We developed a scientific monitoring protocol that is aimed at capturing and quantifying the dynamics and impact of this invasive insect pest as well as the development of its host plant across a heterogeneous landscape. The cornerstone of this comprehensive monitoring system is timely georeferenced data collection on CBB movement, coffee berry infestation, mortality by the fungus Beauveria bassiana, and coffee plant phenology via a mobile electronic data recording application. This electronic data collection system allows field records to be georeferenced through built-in global positioning systems, and is backed by a network of weather stations and records of farm management practices. Comprehensive monitoring of CBB and host plant dynamics is an essential part of an area-wide project in Hawaii to aggregate landscape-level data for research to improve management practices. Coffee agroecosystems in other parts of the world that experience highly variable environmental and socioeconomic factors will also benefit from implementing this protocol, in that it will drive the development of customized integrated pest management (IPM) to manage CBB populations.

Integrated Pest Management of Coffee Berry Borer in Hawaii and Puerto Rico: Current Status and Prospects

The coffee berry borer (CBB), Hypothenemus hampei, is the most significant insect pest of coffee worldwide. Since CBB was detected in Puerto Rico in 2007 and Hawaii in 2010, coffee growers from these islands are facing increased costs, reduced coffee quality, and increased pest management challenges. Here, we outline the CBB situation, and summarize the findings of growers, researchers, and extension professionals working with CBB in Hawaii. Recommendations for the Integrated Pest Management (IPM) program for CBB in Hawaiian Islands and Puerto Rico include: (1) establish a CBB monitoring program, (2) synchronize applications of insecticides with peak flight activity of CBB especially during the early coffee season, (3) conduct efficient strip-picking as soon as possible after harvest and perform pre-harvest sanitation picks in CBB hotspots if needed, (4) establish protocols to prevent the escape of CBB from processing areas and when transporting berries during harvest, and (5) stump prune by blocks. Progress achieved includes the introduction of the mycoinsecticide Beauveria bassiana to coffee plantations, the coordination of area-wide CBB surveys, the establishment and augmentation of native beetle predators, and an observed reduction of CBB populations and increased coffee quality where IPM programs were established. However, CBB remains a challenge for coffee growers due to regional variability in CBB pressures, high costs, and labor issues, including a lack of training and awareness of CBB management practices among growers.

Semiochemical mediated enhancement of males to complement sterile insect technique in management of the tephritid pest Bactrocera tryoni (Froggatt)

Queensland fruit fly, Bactrocera tryoni (Froggatt), is the most significant pest of Australia's $9 billion horticulture industry. The sterile insect technique (SIT) and cue-lure (a synthetic analogue of raspberry ketone (RK))-based male annihilation technique (MAT) are two of the most effective management tools against this pest. However, combining these two approaches is considered incompatible as MAT kills sterile and 'wild' males indiscriminately. In the present study we tested the effect of pre-release feeding of B. tryoni on RK on their post-release survival and response to MAT in field cages and in a commercial orchard. In both settings, survival was higher for RK supplemented adults compared to control (i.e. RK denied) adults. A lower number of RK supplemented sterile males were recaptured in MAT baited traps in both the field cages and orchard trials compared to RK denied sterile males. The advantage of this novel "male replacement" approach (relatively selective mortality of wild males at lure-baited traps while simultaneously releasing sterile males) is increasing the ratio of sterile to wild males in the field population, with potential for reducing the number of sterile males to be released.

To Catch a Fly: Landing and Capture of Ceratitis capitata in a Jackson Trap with and without an Insecticide

Attractant-based traps are a cornerstone of detection, delimitation and eradication programs for pests such as tephritid fruit flies. The ideal trap and lure combination has high attraction (it brings insects to the trap from a distance) and high capture efficiency (it has a high probability of capturing the insect once it arrives at the trap). We examined the effect of an insecticide (DDVP) in combination with a pheromone lure (trimedlure) on capture of Ceratitis capitata using 1) digital images of surfaces of a Jackson trap analyzed via computer vision, and 2) counts of the number of flies caught in the trap and in the area under the trap. Our results indicate no significant difference in trap capture without or with insecticide (means ± SD = 324 ±135 and 356 ±108, respectively). However, significantly more dead flies were found around the trap with insecticide (92 ±53 with insecticide compared with 35 ±22 without), suggesting a possible decrease in trap efficiency due to mortality before insects enter the trap. Indeed, the average number of flies detected on all surfaces of the traps with insecticide was lower than that for lure-only (4.15±0.39 vs 8.30±1.18), and both were higher than control (no lure: 0.76 ±0.08). We found that the majority of fly sightings, 71% of the total, occurred on the inside panels of the lure-only traps, suggesting that increased efficiency of the Jackson trap may be obtained by adding a contact insecticide to those surfaces.

Field Estimates of Attraction of Ceratitis capitata to Trimedlure and Bactrocera dorsalis (Diptera: Tephritidae) to Methyl Eugenol in Varying Environments

Measuring and modeling the attractiveness of semiochemical-baited traps is of significant importance to detection, delimitation, and control of invasive pests. Here, we describe the results of field mark-release-recapture experiments with Ceratitis capitata (Wiedemann) and Bactrocera dorsalis (Hendel) to estimate the relationship between distance from a trap baited with trimedlure and methyl eugenol, respectively, and probability of capture for a receptive male insect. Experiments were conducted using a grid of traps with a central release point at two sites on Hawaii Island, a Macadamia orchard on the East side of the island and a lava field on the West side. We found that for B. dorsalis and methyl eugenol there is a 65% probability of capture at ∼36 m from a single trap, regardless of habitat. For C. capitata, we found a 65% probability of capture at a distance of ∼14 m from a single trap in the orchard and 7 m in the lava field. We also present results on the spatial and temporal pattern of recaptures. The attraction data are analyzed via a hyperbolic secant-based capture probability model.

A computer model of insect traps in a landscape

Attractant-based trap networks are important elements of invasive insect detection, pest control, and basic research programs. We present a landscape-level, spatially explicit model of trap networks, focused on detection, that incorporates variable attractiveness of traps and a movement model for insect dispersion. We describe the model and validate its behavior using field trap data on networks targeting two species, Ceratitis capitata and Anoplophora glabripennis. Our model will assist efforts to optimize trap networks by 1) introducing an accessible and realistic mathematical characterization of the operation of a single trap that lends itself easily to parametrization via field experiments and 2) allowing direct quantification and comparison of sensitivity between trap networks. Results from the two case studies indicate that the relationship between number of traps and their spatial distribution and capture probability under the model is qualitatively dependent on the attractiveness of the traps, a result with important practical consequences.

Characterizing the developmental transcriptome of the oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae) through comparative genomic analysis with Drosophila melanogaster utilizing modENCODE datasets

BACKGROUND

The oriental fruit fly, Bactrocera dorsalis, is an important pest of fruit and vegetable crops throughout Asia, and is considered a high risk pest for establishment in the mainland United States. It is a member of the family Tephritidae, which are the most agriculturally important family of flies, and can be considered an out-group to well-studied members of the family Drosophilidae. Despite their importance as pests and their relatedness to Drosophila, little information is present on B. dorsalis transcripts and proteins. The objective of this paper is to comprehensively characterize the transcripts present throughout the life history of B. dorsalis and functionally annotate and analyse these transcripts relative to the presence, expression, and function of orthologous sequences present in Drosophila melanogaster.

RESULTS

We present a detailed transcriptome assembly of B. dorsalis from egg through adult stages containing 20,666 transcripts across 10,799 unigene components. Utilizing data available through Flybase and the modENCODE project, we compared expression patterns of these transcripts to putative orthologs in D. melanogaster in terms of timing, abundance, and function. In addition, temporal expression patterns in B. dorsalis were characterized between stages, to establish the constitutive or stage-specific expression patterns of particular transcripts. A fully annotated transcriptome assembly is made available through NCBI, in addition to corresponding expression data.

CONCLUSIONS

Through characterizing the transcriptome of B. dorsalis through its life history and comparing the transcriptome of B. dorsalis to the model organism D. melanogaster, a database has been developed that can be used as the foundation to functional genomic research in Bactrocera flies and help identify orthologous genes between B. dorsalis and D. melanogaster. This data provides the foundation for future functional genomic research that will focus on improving our understanding of the physiology and biology of this species at the molecular level. This knowledge can also be applied towards developing improved methods for control, survey, and eradication of this important pest.

Male motion coordination in anopheline mating swarms

The Anopheles gambiae species complex comprises the primary vectors of malaria in much of sub-Saharan Africa. Most of the mating in these species occurs in swarms composed almost entirely of males. Intermittent, organized patterns in such swarms have been observed, but a detailed description of male-male interactions has not previously been available. We identify frequent, time-varying interactions characterized by periods of parallel flight in data from 8 swarms of Anopheles gambiae and 3 swarms of Anopheles coluzzii filmed in 2010 and 2011 in the village of Donéguébogou, Mali. We use the cross correlation of flight direction to quantify these interactions and to induce interaction graphs, which show that males form synchronized subgroups whose size and membership change rapidly. A swarming model with damped springs between each male and the swarm centroid shows good agreement with the correlation data, provided that local interactions represented by damping of relative velocity between males are included.

Stereoscopic video analysis of Anopheles gambiae behavior in the field: challenges and opportunities

Advances in our ability to localize and track individual swarming mosquitoes in the field via stereoscopic image analysis have enabled us to test long-standing ideas about individual male behavior and directly observe coupling. These studies further our fundamental understanding of the reproductive biology of mosquitoes. In addition, our analyses using stereoscopic video of swarms of the African malaria vector Anopheles gambiae have produced results that should be relevant to any "release-based" method of control including Sterile Insect Technique (SIT) and genetically modified male mosquitoes (GMM). The relevance of the results is primarily due to the fact that any mosquito vectors released for control are almost certainly going to be males; further, for SIT, GMM or similar approaches to be successful, the released males will have to successfully locate swarms and then mate with wild females. Thus, understanding and potentially manipulating the mating process could play a key role in future control programs. Our experience points to special challenges created by stereoscopic video of swarms. These include the expected technical difficulties of capturing usable images of mosquitoes in the field, and creating an automated tracking system to enable generation of large numbers of three dimensional tracks over many seconds of footage. Once the data are collected, visualization and application of appropriate statistical and analytic methods also are required. We discuss our recent progress on these problems, give an example of a statistical approach to quantify individual male movement in a swarm with some novel results, and suggest further studies incorporating experimental manipulation and three dimensional localization and tracking of individual mosquitoes in wild swarms.

Review: Improving our knowledge of male mosquito biology in relation to genetic control programmes

The enormous burden placed on populations worldwide by mosquito-borne diseases, most notably malaria and dengue, is currently being tackled by the use of insecticides sprayed in residences or applied to bednets, and in the case of dengue vectors through reduction of larval breeding sites or larviciding with insecticides thereof. However, these methods are under threat from, amongst other issues, the development of insecticide resistance and the practical difficulty of maintaining long-term community-wide efforts. The sterile insect technique (SIT), whose success hinges on having a good understanding of the biology and behaviour of the male mosquito, is an additional weapon in the limited arsenal against mosquito vectors. The successful production and release of sterile males, which is the mechanism of population suppression by SIT, relies on the release of mass-reared sterile males able to confer sterility in the target population by mating with wild females. A five year Joint FAO/IAEA Coordinated Research Project brought together researchers from around the world to investigate the pre-mating conditions of male mosquitoes (physiology and behaviour, resource acquisition and allocation, and dispersal), the mosquito mating systems and the contribution of molecular or chemical approaches to the understanding of male mosquito mating behaviour. A summary of the existing knowledge and the main novel findings of this group is reviewed here, and further presented in the reviews and research articles that form this Acta Tropica special issue.

Spatial dynamics of two oriental fruit fly (Diptera: Tephritidae) parasitoids, Fopius arisanus and Diachasmimorpha longicaudata (Hymenoptera: Braconidae), in a Guava orchard in Hawaii

We examined spatial patterns of both sexes of oriental fruit fly, Bactrocera dorsalis (Hendel), and its two most abundant parasitoids, Fopius arisanus (Sonan) and Diachasmimorpha longicaudata (Ashmead) in a commercial guava (Psidium guajava L.) orchard. Oriental fruit fly spatial patterns were initially random, but became highly aggregated with host fruit ripening and the subsequent colonization of, first, F. arisanus (egg-pupal parasitoid) and, second, D. longicaudata (larval-pupal parasitoid). There was a significant positive relationship between populations of oriental fruit fly and F. arisanus during each of the F. arisanus increases, a pattern not exhibited between oriental fruit fly and D. longicaudata. Generally, highest total numbers of males and females (oriental fruit fly, F. arisanus, and D. longicaudata) occurred on or about the same date. There was a significant positive correlation between male and female populations of all three species; we measured a lag of 2-4 wk between increases of female F. arisanus and conspecific males. There was a similar trend in one of the two years for the second most abundant species, D. longicaudata, but no sign of a time lag between the sexes for oriental fruit fly. Spatially, we found a significant positive relationship between numbers of F. arisanus in blocks and the average number in adjoining blocks. We did not find the same effect for oriental fruit fly and D. longicaudata, possibly a result of lower overall numbers of the latter two species or less movement of F. arisanus within the field.

An agent-based simulation of extirpation of Ceratitis capitata applied to invasions in California

We present an agent-based simulation (ABS) of Ceratitis capitata ("Medfly") developed for estimating the time to extirpation of this pest in areas where quarantines and eradication treatments were immediately imposed. We use the ABS, implemented in the program MED-FOES, to study seven different outbreaks that occurred in Southern California from 2008 to 2010. Results are compared with the length of intervention and quarantine imposed by the State, based on a linear developmental model (thermal unit accumulation, or "degree-day"). MED-FOES is a useful tool for invasive species managers as it incorporates more information from the known biology of the Medfly, and includes the important feature of being demographically explicit, providing significant improvements over simple degree-day calculations. While there was general agreement between the length of quarantine by degree-day and the time to extirpation indicated by MED-FOES, the ABS suggests that the margin of safety varies among cases and that in two cases the quarantine may have been excessively long. We also examined changes in the number of individuals over time in MED-FOES and conducted a sensitivity analysis for one of the outbreaks to explore the role of various input parameters on simulation outcomes. While our implementation of the ABS in this work is motivated by C. capitata and takes extirpation as a postulate, the simulation is very flexible and can be used to study a variety of questions on the invasion biology of pest insects and methods proposed to manage or eradicate such species.

The dance of male Anopheles gambiae in wild mating swarms

An important element of mating in the malaria vector Anopheles gambiae Giles in nature is the crepuscular mating aggregation (swarm) composed almost entirely of males, where most coupling and insemination is generally believed to occur. In this study, we mathematically characterize the oscillatory movement of male An. gambiae in terms of an established individual-based mechanistic model that parameterizes the attraction of a mosquito toward the center of the swarm using the natural frequency of oscillation and the resistance to its motion, characterized by the damping ratio. Using three-dimensional trajectory data of ten wild mosquito swarms filmed in Mali, Africa, we show two new results for low and moderate wind conditions, and indicate how these results may vary in high wind. First, we show that in low and moderate wind the vertical component of the mosquito motion has a lower frequency of oscillation and higher damping ratio than horizontal motion. In high wind, the vertical and horizontal motions are similar to one another and the natural frequencies are higher than in low and moderate wind. Second, we show that the predicted average disagreement in the direction of motion of swarming mosquitoes moving randomly is greater than the average disagreement we observed between each mosquito and its three closest neighbors, with the smallest level of disagreement occurring for the nearest neighbor in seven out of 10 swarms. The alignment of the direction of motion between nearest neighbors is the highest in high wind. This result provides evidence for flight-path coordination between swarming male mosquitoes.

Seasonal climate effects anemotaxis in newly emerged adult Anopheles gambiae Giles in Mali, West Africa

The direction and magnitude of movement by the malaria vector Anopheles gambiae Giles has been of great interest to medical entomologists for over 70 years. This direction of movement is likely to be affected by many factors, from environmental conditions and stage of life history of the mosquito to the existence of attractants in the vicinity. We report here the direction of movement of newly emerged An. gambiae in nature, around the village of Donéguébougou, Mali. We assessed the direction of movement for individual mosquitoes by placing them in a novel enclosure with exit traps oriented in the direction of the cardinal and intermediate points of the compass. We consistently found predominantly Southward directions of movement during 2009 and 2010, with an additional Eastward component during the dry season and a Westward one during the wet season. Our data indicate that wind has an important effect on the direction of movement, but that this effect varied by season: Average directions of movement were downwind during the dry season and upwind during the wet season. A switch in anemotactic response suggests that the direction of movement of An. gambiae relative to the wind immediately after emergence under varying conditions of humidity should be further investigated under controlled conditions.

A further insight into the sialome of the tropical bont tick, Amblyomma variegatum

Background

Ticks--vectors of medical and veterinary importance--are themselves also significant pests. Tick salivary proteins are the result of adaptation to blood feeding and contain inhibitors of blood clotting, platelet aggregation, and angiogenesis, as well as vasodilators and immunomodulators. A previous analysis of the sialotranscriptome (from the Greek sialo, saliva) of Amblyomma variegatum is revisited in light of recent advances in tick sialomes and provides a database to perform a proteomic study.

Results

The clusterized data set has been expertly curated in light of recent reviews on tick salivary proteins, identifying many new families of tick-exclusive proteins. A proteome study using salivary gland homogenates identified 19 putative secreted proteins within a total of 211 matches.

Conclusions

The annotated sialome of A. variegatum allows its comparison to other tick sialomes, helping to consolidate an emerging pattern in the salivary composition of metastriate ticks; novel protein families were also identified. Because most of these proteins have no known function, the task of functional analysis of these proteins and the discovery of novel pharmacologically active compounds becomes possible.

Population size and migration of Anopheles gambiae in the Bancoumana Region of Mali and their significance for efficient vector control

We present results of two intensive mark-release-recapture surveys conducted during the wet and dry seasons of 2008 in the villages of Fourda and Kenieroba, Mali. The former is a small fishing village by the Niger River with a moderate to high densities of Anopheles gambiae Giles s.s. (Diptera: Culicidae) throughout the year, while the latter is a large agricultural community 2 km inland that experiences strong seasonal fluctuation in An. gambiae densities. We estimate the population size of female An. gambiae in Fourda to be in less than 3,000 during the dry season. We found evidence of large population size and migration from Fourda in Kenieroba during the wet season, but very low numbers and no sign of migrants during the dry season. We suggest that malaria vector control measures aimed at adult mosquitoes might be made more efficient in this region and other seasonal riparian habitats by targeting disruption of mosquito populations by the river during the dry season. This would decrease the size of an already small population, and would be likely to delay the explosive growth in vector numbers in the larger inland villages as rainfall increases.

Spatial swarm segregation and reproductive isolation between the molecular forms of Anopheles gambiae

Anopheles gambiae, the major malaria vector in Africa, can be divided into two subgroups based on genetic and ecological criteria. These two subgroups, termed the M and S molecular forms, are believed to be incipient species. Although they display differences in the ecological niches they occupy in the field, they are often sympatric and readily hybridize in the laboratory to produce viable and fertile offspring. Evidence for assortative mating in the field was recently reported, but the underlying mechanisms awaited discovery. We studied swarming behaviour of the molecular forms and investigated the role of swarm segregation in mediating assortative mating. Molecular identification of 1145 males collected from 68 swarms in Donéguébougou, Mali, over 2 years revealed a strict pattern of spatial segregation, resulting in almost exclusively monotypic swarms with respect to molecular form. We found evidence of clustering of swarms composed of individuals of a single molecular form within the village. Tethered M and S females were introduced into natural swarms of the M form to verify the existence of possible mate recognition operating within-swarm. Both M and S females were inseminated regardless of their form under these conditions, suggesting no within-mate recognition. We argue that our results provide evidence that swarm spatial segregation strongly contributes to reproductive isolation between the molecular forms in Mali. However this does not exclude the possibility of additional mate recognition operating across the range distribution of the forms. We discuss the importance of spatial segregation in the context of possible geographic variation in mechanisms of reproductive isolation.

Structure and dynamics of male swarms of Anopheles gambiae

Mosquito swarms are poorly understood mating aggregations. In the malaria vector Anopheles gambiae Giles, they are known to depend on environmental conditions, such as the presence of a marker on the ground, and they may be highly relevant to reproductive isolation. We present quantitative measurements of individual An. gambiae positions within swarms from Donéguébougou, Mali, estimated by stereoscopic video image analysis. Results indicate that swarms in this species are approximately spherical, with an unexpectedly high density of individuals close to the swarm centroid. This high density may be the result of individual males maximizing their probability of encountering a female or a product of mosquito orientation through cues within the swarm. Our analysis also suggests a difference in swarm organization between putative incipient species of An. gambiae with increasing numbers of males. This may be related to a difference in marker use between these groups, supporting the hypothesis that swarming behavior is a mechanism of mate recognition and ultimately reproductive isolation.

FORMATOMATIC: a program for converting diploid allelic data between common formats for population genetic analysis

There has been a great increase in both the number of population genetic analysis programs and the size of data sets being studied with them. Since the file formats required by the most popular and useful programs are variable, automated reformatting or conversion between them is desirable. formatomatic is an easy to use program that can read allelic data files in genepop, raw (csv) or convert formats and create data files in nine formats: raw (csv), arlequin, genepop, immanc/bayesass +, migrate, newhybrids, msvar, baps and structure. Use of formatomatic should greatly reduce time spent reformatting data sets and avoid unnecessary errors.

Is vector body size the key to reduced malaria transmission in the irrigated region of Niono, Mali?

Malaria vectors can reach very high densities in villages near irrigated rice fields in Africa, leading to the expectation that malaria should be especially prevalent there. Surprisingly, this is not always the case. In Niono, Mali, villages from nonirrigated areas have higher malaria prevalence than those within the irrigated regions, which suffer from higher mosquito numbers. One hypothesis explaining this observation is that mosquitoes from irrigated fields with high densities are inefficient vectors. This could occur if higher larval densities lead to smaller mosquitoes that suffer elevated mortality. Three predictions of the hypothesis were studied. First, the effect of larval density on larval body size was measured for both Anopheles gambiae Giles and Anopheles funestus Giles. Second, the relationship between larval and adult body size was tested. Third, evidence of an effect of adult size on survivorship in both irrigated and nonirrigated villages during the wet and dry seasons was sought. There was a modest positive relationship between densities of immatures and larval size, and a strong relationship between larval and adult size. Furthermore, adult survivorship was higher in nonirrigated areas. However, there was no effect of size on survivorship between comparable samples from both the irrigated and nonirrigated zones. Although density may have a causal relationship with reduced transmission in the irrigated areas of Niono, it is unlikely to be because higher density leads to smaller body size and lower survivorship.