Diversity and Genetic Reassortment of Keystone Virus in Mosquito Populations in Florida

Keystone orthobunyavirus (KEYV), a member of the genus Orthobunyavirus, was first isolated in 1964 from mosquitoes in Keystone, Florida. Although data on human infections are limited, the virus has been linked to a fever/rash syndrome and, possibly, encephalitis, with early studies suggesting that 20% of persons in the Tampa, Florida, region had antibodies to KEYV. To assess the distribution and diversity of KEYV in other regions of Florida, we collected > 6,000 mosquitoes from 43 sampling sites in St. Johns County between June 2019 and April 2020. Mosquitoes were separated into pools by species and collection date and site. All pools with Aedes spp. (293 pools, 2,171 mosquitoes) were screened with a real-time reverse transcriptase polymerase chain reaction (rRT-PCR) assay that identifies KEYV and other closely related virus species of what was previously designated as the California encephalitis serogroup. In 2020, screening for KEYV was expanded to include 211 pools of Culex mosquitoes from sites where KEYV-positive Aedes spp. had been identified. rRT-PCR-positive samples were inoculated into cell cultures, and five KEYV isolates from Aedes atlanticus pools were isolated and sequenced. Analyses of the KEYV large genome segment sequences revealed two distinct KEYV clades, whereas analyses of the medium and small genome segments uncovered past reassortment events. Our data documented the ongoing seasonal circulation of multiple KEYV clades within Ae. atlanticus mosquito populations along the east coast of Florida, highlighting the need for further studies of the impact of this virus on human health.

Developing the radiation-based sterile insect technique (SIT) for controlling Aedes aegypti: identification of a sterilizing dose

BACKGROUND

The sterile insect technique (SIT) is emerging as a tool to supplement traditional pesticide-based control of Aedes aegypti, a prominent mosquito vector of microbes that has increased the global burden of human morbidity and mortality over the past 50 years. SIT relies on rearing, sterilizing and releasing large numbers of male mosquitoes that will mate with fertile wild females, thus reducing production of offspring from the target population. In this study, we investigated the effects of ionizing radiation (gamma) on male and female survival, longevity, mating behavior, and sterility of Ae. aegypti in a dose-response design. This work is a first step towards developing an operational SIT field suppression program against Ae. aegypti in St. Augustine, Florida, USA.

RESULTS

Exposing late-stage pupae to 50 Gy of radiation yielded 99% male sterility while maintaining similar survival of pupae to adult emergence, adult longevity and male mating competitiveness compared to unirradiated males. Females were completely sterilized at 30 Gy, and when females were dosed with 50 Gy, they had a lower incidence of blood-feeding than unirradiated females.

CONCLUSION

Our work suggests that an ionizing radiation dose of 50 Gy should be used for future development of operational SIT in our program area because at this dose males are 99% sterile while maintaining mating competitiveness against unirradiated males. Furthermore, females that might be accidentally released with sterile males as a result of errors in sex sorting also are sterile and less likely to blood-feed than unirradiated females at our 50 Gy dose. © 2022 Society of Chemical Industry.

A systematic review of published literature on mosquito control action thresholds across the world

BACKGROUND

Despite the use of numerous methods of control measures, mosquito populations and mosquito-borne diseases are still increasing globally. Evidence-based action thresholds to initiate or intensify control activities have been identified as essential in reducing mosquito populations to required levels at the correct/optimal time. This systematic review was conducted to identify different mosquito control action thresholds existing across the world and associated surveillance and implementation characteristics.

METHODOLOGY/PRINCIPAL FINDINGS

Searches for literature published from 2010 up to 2021 were performed using two search engines, Google Scholar and PubMed Central, according to PRISMA guidelines. A set of inclusion/exclusion criteria were identified and of the 1,485 initial selections, only 87 were included in the final review. Thirty inclusions reported originally generated thresholds. Thirteen inclusions were with statistical models that seemed intended to be continuously utilized to test the exceedance of thresholds in a specific region. There was another set of 44 inclusions that solely mentioned previously generated thresholds. The inclusions with "epidemiological thresholds" outnumbered those with "entomological thresholds". Most of the inclusions came from Asia and those thresholds were targeted toward Aedes and dengue control. Overall, mosquito counts (adult and larval) and climatic variables (temperature and rainfall) were the most used parameters in thresholds. The associated surveillance and implementation characteristics of the identified thresholds are discussed here.

CONCLUSIONS/SIGNIFICANCE

The review identified 87 publications with different mosquito control thresholds developed across the world and published during the last decade. Associated surveillance and implementation characteristics will help organize surveillance systems targeting the development and implementation of action thresholds, as well as direct awareness towards already existing thresholds for those with programs lacking available resources for comprehensive surveillance systems. The findings of the review highlight data gaps and areas of focus to fill in the action threshold compartment of the IVM toolbox.

Better than DEET Repellent Compounds Derived from Coconut Oil

Hematophagous arthropods are capable of transmitting human and animal pathogens worldwide. Vector-borne diseases account for 17% of all infectious diseases resulting in 700,000 human deaths annually. Repellents are a primary tool for reducing the impact of biting arthropods on humans and animals. N,N-Diethyl-meta-toluamide (DEET), the most effective and long-lasting repellent currently available commercially, has long been considered the gold standard in insect repellents, but with reported human health issues, particularly for infants and pregnant women. In the present study, we report fatty acids derived from coconut oil which are novel, inexpensive and highly efficacious repellant compounds. These coconut fatty acids are active against a broad array of blood-sucking arthropods including biting flies, ticks, bed bugs and mosquitoes. The medium-chain length fatty acids from C_8:0 to C_12:0 were found to exhibit the predominant repellent activity. In laboratory bioassays, these fatty acids repelled biting flies and bed bugs for two weeks after application, and ticks for one week. Repellency was stronger and with longer residual activity than that of DEET. In addition, repellency was also found against mosquitoes. An aqueous starch-based formulation containing natural coconut fatty acids was also prepared and shown to protect pastured cattle from biting flies up to 96-hours in the hot summer, which, to our knowledge, is the longest protection provided by a natural repellent product studied to date.

Sublethal effects of a vapour-active pyrethroid, transfluthrin, on Aedes aegypti and Ae. albopictus (Diptera: Culicidae) fecundity and oviposition behaviour

BACKGROUND

It is assumed that mosquitoes surviving exposure to spatial repellents when attempting to bite a host will not have significant adverse impacts on their downstream biology. Therefore, a critical knowledge gap is understanding the extent to which sublethal exposure to volatile pyrethroids may damage the performance of mosquitoes that survive exposure to vapour-active pyrethroids. To address this, laboratory-reared Aedes aegypti (L.) and Ae. albopictus (Skuse) were exposed to one of three sublethal concentrations of transfluthrin before being offered a blood-meal, after which their survival, fecundity, fertility, and egg-laying behaviour was assessed.

RESULTS

Both species expressed reduced skip-oviposition behaviour at all exposures. Both species also suffered a major reduction in viable eggs (50-75% reduction in viable eggs laid). A phenotype where eggs collapsed after laying was observed in Ae. aegypti, and this response increased with exposure concentrations. Dissected females of both species retained 50% or fewer of their eggs, with Ae. albopictus retaining a significant proportion of melanised oocytes following the highest exposure.

CONCLUSIONS

Our findings suggest that volatile pyrethroids can reduce skip-oviposition, which may improve source reduction outcomes during integrated management. The additional fecundity reduction caused by sublethal exposures to volatile pyrethroids improves our confidence in recommending them for urban vector management. Furthermore, we suggest that volatile pyrethroids should be adapted into delivery methods compatible with mosquito abatement programs.

Evaluation of the Honey-Card Technique for Detection of Transmission of Arboviruses in Florida and Comparison With Sentinel Chicken Seroconversion

Zoonotic mosquito-borne viruses, such as the West Nile virus (WNV) and eastern equine encephalitis virus (EEEV), are major public health threats in the United States. Early detection of virus transmission and targeted vector management are critical to protect humans against these pathogens. Sentinel chickens and pool screening of mosquitoes, the most widely used methods of arbovirus early detection, have technical time-lags that compromise their early-detection value. The exploitation of sugar-feeding by trapped mosquitoes for arbovirus surveillance may represent a viable alternative to other methods. Here we compared effectiveness of sugar-impregnated nucleic-acid preserving substrates (SIPS) and sentinel chicken program for detecting WNV, EEEV, and St. Louis encephalitis virus in gravid traps, CO₂-baited light traps, and resting traps at 10 locations in two Florida counties. In St. Johns County, comparable numbers of EEEV detections were made by SIPS traps (18) and sentinel chickens (22), but fewer WNV detections were made using SIPS (1) than sentinel chickens (13). In Volusia County, seven arbovirus detections were made via the sentinel chicken program (one EEEV and six WNV), whereas only one arbovirus detection (WNV) was made using SIPS. CO₂-baited light traps captured >90% of total mosquitoes, yet yielded <30% of arbovirus detections. Resting traps and gravid traps captured a fraction of total mosquitoes, yet yielded roughly equivalent numbers of arbovirus detections, as did light traps. Challenges to successful deployment of SIPS include optimization of traps for collecting all vector species, increasing sugar-feeding rates of trapped vectors, and developing tractable methods for arbovirus detection.

Efficacy of attractive toxic sugar baits (ATSB) against Aedes albopictus with garlic oil encapsulated in beta-cyclodextrin as the active ingredient

We tested the efficacy of attractive toxic sugar bait (ATSB) with garlic oil microencapsulated in beta-cyclodextrin as active ingredient against Aedes albopictus in suburban Haifa, Israel. Two three-acre gardens with high numbers of Ae. albopictus were selected for perimeter spray treatment with ATSB and ASB (bait containing no active ingredient). Baits were colored with food dye to verify feeding of the mosquitoes. The mosquito population was monitored by human landing catches and sweep net catches in the surrounding vegetation. Experiments lasted for 44 days. Treatment occurred on day 13. The mosquito population collapsed about 4 days after treatment and continued to drop steadily for 27 days until the end of the study. At the experimental site the average pre-treatment landing rate was 17.2 per 5mins. Two days post-treatment, the landing rate dropped to 11.4, and continued to drop to an average of 2.6 during the following 26 days. During the same period, the control population was stable. Few sugar fed females (8-10%) approached a human bait and anthrone tests showed relatively small amounts of sugar within their crop/gut. Around 60-70 % of males caught near our human bait were sugar positive which may indicate that the males were feeding on sugar for mating related behavior. From the vegetation treated with the toxic bait, we recovered significantly fewer (about 10-14%) males and females stained by ATSB than at the ASB-treated control. This may indicate that the toxic baits alter the resting behavior of the poisoned mosquitoes within the vegetation. Almost no Ae. albopictus females (5.2±1.4) approached human bait after treatment with ATSB. It therefore appears that microencapsulated garlic oil is an effective pesticide against Ae. albopictus when used in an ATSB system.

Altered behavioral responses of Sindbis virus-infected Aedes aegypti (Diptera: Culicidae) to DEET and non-DEET based insect repellents

Changes in the time to first bite (TFB) and the bloodfeeding behavior of adult female Aedes aegypti (L.) mosquitoes following dissemination of Sindbis virus (SINV) were observed after exposure to repellents with the active ingredients (AI) DEET, picaridin, 2-undecanone (2-U), and oil of lemon eucalyptus. Dissemination of SINV significantly decreased (P<0.0001) the TFB of DEET (15%) and picaridin (15%) by 46% and 37%, respectively. Significant (P<0.0001) changes in activation, probing, and engorgement times were observed in SINV infected mosquitoes after exposure to the four repellents compared to uninfected mosquitoes. Taken together, a decrease in TFB and time to complete the four bloodfeeding stages will lessen the prey-status, and enhance both the chances of mosquito survival and arbovirus transmission.

Reversible changes in brain glucose metabolism following thyroid function normalization in hyperthyroidism

BACKGROUND AND PURPOSE

Patients with hyperthyroidism frequently present with regional cerebral metabolic changes, but the consequences of endocrine-induced brain changes after thyroid function normalization are unclear. We hypothesized that the changes of regional cerebral glucose metabolism are related to thyroid hormone levels in patients with hyperthyroid, and some of these changes can be reversed with antithyroid therapy.

MATERIALS AND METHODS

Relative regional cerebral glucose metabolism was compared between 10 new-onset untreated patients with hyperthyroidism and 20 healthy control participants by using brain FDG-PET scans. Levels of emotional distress were evaluated by using the SAS and SDS. Patients were treated with methimazole. A follow-up PET scan was performed to assess metabolic changes of the brain when thyroid functions normalized.

RESULTS

Compared with controls, patients exhibited lower activity in the limbic system, frontal lobes, and temporal lobes before antithyroid treatment. There were positive correlations between scores of depression and regional metabolism in the cingulate and paracentral lobule. The severity of depression and anxiety covaried negatively with pretreatment activity in the inferior temporal and inferior parietal gyri respectively. Compared with the hyperthyroid status, patients with normalized thyroid functions showed an increased metabolism in the left parahippocampal, fusiform, and right superior frontal gyri. The decrease in both FT3 and FT4 was associated with increased activity in the left parahippocampal and right superior frontal gyri.

CONCLUSIONS

The changes of regional cerebral glucose metabolism are related to thyroid hormone levels in patients with hyperthyroidism, and some cerebral hypometabolism can be improved after antithyroid therapy.

Control of Culex quinquefasciatus in a storm drain system in Florida using attractive toxic sugar baits

Attractive toxic sugar baits (ATSBs) were used to control mosquitoes in the storm drains of a residential area on the outskirts of St Augustine, Florida. The drainage system was newly constructed and no mosquitoes were breeding inside it. The area covered by the storm drains was divided in half; 10 drains served as control drains and 16 drains served as experimental drains. The baits, which consisted of a mixture of brown sugar, fruit juice, green dye marker and boric acid, were presented at the entrances of the treated drains and exit traps were positioned over the drain openings and the connecting tubes leading to retention ponds. Similar baits with orange dye and without toxin were presented at the entrances of control drains. A total of 220 pupae of Culex quinquefasciatus (Diptera: Culicidae) were released in each control and toxin-treated drain, and the numbers of recovered mosquitoes were examined to determine the effectiveness of ATSBs in the storm drain system. An average of 178.2 mosquitoes exited each drain in the control area; 87.0% of these had fed on the baits and were stained orange, whereas 13.0% were unstained. In the toxin-treated drains, 83.7% of hatched females and 86.6% of hatched males were controlled by the baits.

Laboratory and field evaluation of insect repellents as larvicides against the mosquitoes Aedes albopictus and Anopheles albimanus

Acute toxicity and persistence of three insect repellents, deet and two piperidines (AI3-35765 and AI3-37220), were evaluated against mosquito larvae of Aedes albopictus (Skuse) and Anopheles albimanus Wiedemann (Diptera: Culicidae) in the laboratory, and against natural populations of Ae. albopictus in the field. In laboratory studies, the LC50 values of the repellents for first instars ranged between 0.005 and 0.021% (Ae. albopictus) and between 0.01 and 0.014% (An. albimanus) and, for fourth instars, between 0.019 and 0.034% (Ae. albopictus) and between 0.015 and 0.024% (An. albimanus). A 0.1% concentration of deet caused 90-100% mortality in first-instar Ae. albopictus for 4 weeks, whereas AI3-35765 and AI3-37220 at the same concentration killed 95-100% of larvae for 12 weeks and 98-100% of larvae for 33 weeks post-treatment, respectively. Deet and AI3-35765 at 0.1 % concentration resulted in complete mortality of first-instar An. albimanus for 3 weeks post-treatment, whereas AI3-37220 resulted in 91-99% larval mortalities for 35 weeks post-treatment. A 0.1% concentration of A13-37220 provided 77-98% larval mortality for 20 weeks and 63-97% larval mortality for 12 weeks post-treatment, respectively, against fourth-instar Ae. albopictus and An. albimanus. In the field, in artificial containers, the reduction of Ae. albopictus larvae caused by deet, AI3-35765 and AI3-37220 was 88-95% for 3-4 weeks, 98-100% for 7 weeks, and 82-100% for 13 weeks post-treatment, respectively. In used tyres, the same concentration of the repellents resulted in 100% reduction of Ae. albopictus larvae for 2 weeks (deet), 4 weeks (AI3-35765) and 5 weeks (AI3-37220) post-treatment. In cemetery flower vases, Aedes spp. larvae were eliminated for 4 weeks (deet) and 6 weeks post-treatment by both A13-35765 and AI3-37220. These topical repellents (particularly AI3-37220) have good potential for development and use in the management of container-inhabiting mosquitoes because they deter oviposition and kill larvae.

Laboratory and field evaluation of insect repellents as oviposition deterrents against the mosquito Aedes albopictus

Three experimental approaches were used to evaluate the oviposition deterrency of three insect repellents, AI3-35765, AI3-37220 (piperidine compounds), and the standard N,N-diethyl-3-methylbenzamide (deet) to the mosquito Aedes albopictus Skuse (Diptera: Culicidae). Against laboratory-reared Ae. albopictus gravid females, the EC50 values of AI3-37220, AI3-35765 and deet were 0.004%, 0.008% and 0.011% in laboratory cages and 0.004%, 0.01% and 0.009% in an outdoor screened cage. For a natural population of Ae. albopictus tested in the field, the EC50 values were determined as 0.004%, 0.008% and 0.001%, respectively. Ageing concentrations of 0.1% of each repellent provided >50% effective oviposition deterrency against the laboratory population of Ae. albopictus for 13 days in laboratory cages, for 15 days in the outdoor cage, and for 21 days against field population of Ae. albopictus in Florida. These topical skin repellents are effective oviposition deterrents for Ae. albopictus when employed at relatively low application rates.

Effects of partial blood engorgement and pretest carbohydrate availability on the repellency of deet to Aedes albopictus

The pretest availability of 10% sucrose solution and/or partial blood engorgement in Aedes albopictus Skuse significantly influenced mosquito attack rates and the time of repellent protection in laboratory bioassays. In 46 cm L x 38 cm W x 37 cm H cages used in USDA repellent tests, non-blood-fed and partially blood-fed mosquitoes attempted to bite at similar rates. In small cages (5 cm dia. x 4 cm H), holding individual females, mean mosquito attack rates were reduced when females were partially blood fed, compared with those not blood fed. The protection period from bites by Ae. albopictus using 25% ethanolic deet (N,N diethyl-3-methylbenzamide) increased significantly in small and USDA standard cages when females had pretest access to sucrose solution, compared with females starved for 12 h. Partial blood engorgement in mosquitoes affected repellent protection time in USDA standard test cages but not in small cages.

Larval case-making behavior of a pestiferous chironomid, Glyptotendipes paripes (Diptera: Chironomidae), with sand grains of different sizes

Field-collected 4th-instar Glyptotendipes paripes larvae from a natural lake in central Florida preferred small-sized (< 0.84-1.99-mm-diam) grains of sand to burrow in and make cases in the laboratory. The larvae buried or formed cases within 3 h of introduction into 120-ml paper cups containing 80 ml tap water and 20 g of the small-diameter sand. When placed in sand with grains of different size ranges, 98-100% of the larvae constructed cases in sand < 0.84 mm in diameter, whereas 86% of these larvae built cases in 0.85-1.99-mm-diam sand. The larvae were unable to construct any recognizable cases in coarser sand (2-3-mm diam). The lengths of cases built with smaller sand grains were significantly longer than those constructed in the larger grains used in the experiment. For laboratory colonization and insecticidal bioassay purposes using G. paripes larvae, sand grains < 0.84 mm in diameter should be utilized for better acclimation of the larvae.

Diel patterns of pupation, emergence, and oviposition in a laboratory population of Aedes albopictus

There was no apparent daily pattern of pupation in Aedes albopictus in the laboratory [14:10 h (L:D); lights on: 0600 h, lights off: 2000 h], but diel patterns of emergence and oviposition were influenced by mosquito body size. Emergence rate was highest in large-bodied male mosquitoes at 1600 h and in small males at 1000 h but was lowest in large and small males, respectively, at 2400 h and 0200 h. Peak emergence of females was at 1600 h, regardless of body size; lowest emergence was at 0400 h. Half of all ovipositions by large females in their first gonotrophic cycle (GC1) were at 2000 and 2200 h but at 1800 to 2000 h in the second gonotrophic cycle (GC2). In small females, oviposition in GC1 and GC2 was highest at 1800 and 1600 h, respectively, and lowest at 0400 h. Half of all ovipositions in small females were at 1600 to 1800 h.

Human host avidity in Aedes albopictus: influence of mosquito body size, age, parity, and time of day

Diel patterns of human host attack by Aedes albopictus in the laboratory were studied in relation to mosquito body size, age, parity, and time of day. Analysis of responses in 10-, 15-, and 20-day-old females indicated a significant main effect due to time of observation in the diel period, as well as significant time x parity and time x age interactions. The distribution of mean host attack responses during the diel period was bimodal with approximately 70% of all activity during photophase (0800-2000 h); attack rates were highest in the morning (0800 h) and evening (1400-2000 h) and lowest between 0200 and 0600 h. The diel pattern of attack responses was bimodal for nulliparous and parous females, but parous females were more active than nulliparous females between 1400 and 2000 h. This pattern became increasingly bimodal during photophase, as mosquitoes aged, regardless of mosquito body size or parity. Variations in host avidity patterns between young and old females suggest that mosquito repellent bioassays initiated early in the day, that last > or = 6 h, or that use young females (approximately 5 days old) overestimate the protection period of deet against mosquitoes > 10 days old.

Age and body size effects on blood meal size and multiple blood feeding by Aedes aegypti (Diptera: Culicidae)

Ten-day-old, parous Aedes aegypti (L.) had a higher threshold of blood meal size for the inhibition of continued host-seeking than did 5 d-old, nulliparous females of the same size. Older females of a smaller-bodied cohort had a higher threshold of blood meal size for the initiation of egg development than did younger females. In contrast, older larger-sized females had a lower blood meal-size threshold for egg development. The blood of paired avian hosts was marked with rubidium and cesium to study the effect of age and body size on the frequency of multiple blood feeding. Chronologically old females had a higher frequency of multiple blood feeding than younger females. In the laboratory, the frequency of multiple blood feeding among larger-sized females was higher than among small-sized females.

Comparative toxicity of selected larvicides and insect growth regulators to a Florida laboratory population of Aedes albopictus

Five organophosphates (OPs) (chlorpyrifos, chlorpyrifos methyl, fenthion, malathion, and temephos), 3 pyrethroids (bifenthrin, cypermethrin, and permethrin), and 2 microbial pesticides (Bacillus thuringiensis serovar.israelensis [B.t.i.] and Bacillus sphaericus) were tested as larvicides against a Florida Aedes albopictus population colonized in the laboratory. In addition, 3 insect growth regulators (IGRS) (diflubenzuron, methoprene, and pyriproxyfen) were evaluated. All OPs, except for malathion, were highly effective as indicated by low LC90s ranging from 0.0069 ppm (chlorpyrifos) to 0.026 ppm (fenthion); the larvae were considered tolerant to malathion (LC90 = 1.043 ppm). LC90 values of pyrethroids were: 0.0175 ppm (bifenthrin), 0.0079 ppm (cypermethrin), and 0.0031 ppm (permethrin). Commercial products of B.t.i., Vectobac and Bactimos were considered economically effective against Ae. albopictus larvae but products of B. sphaericus were ineffective (LC90s > 28 ppm). The IGRs showed exceptional activity. Pyriproxyfen (LC90 = 0.000376 ppm), was 2.23 and 21.5 times more toxic than diflubenzuron and methoprene, respectively. In general, toxicity ranking of chemicals and microbials tested was: IGRs > pyrethroids > OPs > microbials.

Influence of body size and age of Aedes albopictus on human host attack rates and the repellency of deet

Human host attack rates and the repellency of deet (25% in ethanol) to nulliparous Aedes albopictus in the laboratory were significantly influenced (P = 0.05) by mosquito age and body size and by the interaction of age and body size. Host attack rates were higher for 20-day- (24.5%) and 15-day-old females (22.9%) than for 10- (15.1%) and 5-day-old females (11.0%), regardless of body size, and for large females (22.2%) compared with small females (16.6%), regardless of mosquito age. Deet on human skin repelled small-bodied females longer (3.87 h) than large females (2.31 h); 15-day-old females were repelled longer (3.75 h) than 5- (2.33 h), 10- (3.08 h), or 20-day-old females (3.07 h), regardless of body size. Host attack rates and deet repellency among 15-day-old parous and 15-day-old nulliparous large- and small-bodied female Ae. albopictus were similar but deet repellency was less (by approximately 2 h) against large females compared with small-bodied females.

Evaluation of granular corncob formulations of Bacillus thuringiensis serovar israelensis against mosquito larvae using a semi-field bioassay method

A semi-field bioassay method using commonly available laundry tubs evaluated efficacy and residual activity of 6 granular corncob formulations of Bacillus thuringiensis serovar israelensis against laboratory-reared late 3rd- and early 4th-instar larvae of Aedes taeniorhynchus introduced to the tubs. These formulations produced appreciable larval mortalities (up to 75%) for 9 days posttreatment, with indications of having more prolonged activity. The consistent posttreatment larval mortality trends and the elucidated efficacy differences between formulations suggest that this bioassay method for the granular formulations is reliable and reproducible.

Oviposition, hatching, and age composition of a pestiferous midge, Glyptotendipes paripes (Diptera: Chironomidae)

Field-caught gravid female Glyptotendipes paripes in central Florida laid a single egg mass each during onset of photophase in laboratory cages. Egg masses averaged 626 and 942 eggs/mass during summer and spring, respectively. Oviposition preference in water was not detected when provided from different sources (i.e., distilled, tap, ponds and a lake). However, the percentage of egg hatch/mass was significantly (P < 0.05) higher in the lake water than in water from the other 3 sources. Observations on follicular development in the ovaries indicated presence of 1/2-3/4 yolk within 2 days, full yolk at > or = 2 days, and parity at > or = 4 days postemergence. Age composition of field-collected G. paripes populations from June to December 1992 was 29% at < 2, 48% at > or = 2, and 23% at > or = 4 days old, and parity 23%. Adult abundance was correlated with prevailing air temperatures in the study area.

Relationship between wing length and fecundity of a pestiferous midge, Glyptotendipes paripes (Diptera: Chironomidae)

The relationship between body size and fecundity of adult female Glyptotendipes paripes collected along southern shore areas of Lake Monroe, Sanford, FL, was studied by measuring wing length and examining ovaries, follicular development, and number of eggs/egg mass. Wing length of nulliparous, as well as parous females, had a significant (P < 0.01) linear relationship with dry body weight. Large females had a significantly (P < 0.01) higher number of follicles and eggs/egg mass than small females. No correlation existed between wing length and parity nor between wing length and age composition of field populations sampled between January and June 1993.

Efficacy of two formulations of the insect growth regulator, pyriproxyfen (Nylar or Sumilarv), against nuisance Chironomidae (Diptera) in man-made ponds

A juvenoid insect growth regulator, pyriproxyfen (Nylar or Sumilarv), in a 10% emulsifiable concentrate (10 EC) and a granular (3% sand granules) formulation was evaluated for efficacy against natural populations of chironomid midges in man-made ponds in central Florida. Both formulations at 0.05 kg AI/ha induced complete suppression of adult midge emergence for 1 wk. At 0.2 kg AI/ha, emergence of adult midges completely ceased for 2 and 5 wk with the EC and the granules, respectively. The EC formulation was not effective beyond 2 wk, but the granules at both treatment rates reduced midge emergence by 81-100% for 9 wk posttreatment. The differences in suppression of adult midge emergence between the 2 formulations and times posttreatment were both highly significant (P < 0.01). No significant difference (P > 0.05) was found between the posttreatment percent inhibition of midge emergence caused by the lower and the higher rates of the granular formulation. Some reductions of midge larvae occurred in the ponds receiving the higher rate of the 2 formulations, but these reductions were statistically not significant.