New distribution of Reticulitermes speratus speratus (Blattodea: Rhinotermitidae) in Korea

Reticulitermes speratus (Kolbe) is economically important pest in East Asia including Korea, Japan, and China where they infest wooden structures in urban areas. Previously, it has been reported that R. speratus consists of 5 subspecies, R. speratus kyushuensis Morimoto, R. speratus speratus Kolbe, R. speratus leptolabralis Morimoto, R. speratus okinawanus Morimoto, R. speratus yaeyamanus Morimoto, while only R. speratus kyushuensis was recorded in Korea in the past. However, it remains elusive if different subspecies of R. speratus other than R. speratus kyushuensis are present in Korea. In this study, we report the first record of R. speratus speratus from Korea, which was verified using soldier morphology and molecular characteristics obtained from a mitochondrial gene. R. speratus speratus Kolbe, 1885 (Blattodea: Rhinotermitidae) are found in several provinces, mainly southern regions in Korea, whereas R. speratus kyushuensis are distributed throughout the country. Our morphological comparison showed that R. speratus speratus can be distinguishable from R. speratus kyushuensis by the ratio of the posterior postmentum width to length. In the molecular comparison, R. speratus speratus revealed genetic differences of 3.06% (range 2.60-4.10%) from R. speratus kyushuensis using cytochrome oxidase subunit II gene sequences.

Trichoderma metabolites trigger aggregation behavior in Formosan subterranean termites (Coptotermes formosanus)

Our previous studies have shown that some Trichoderma fungi trigger aggregation behavior in Formosan subterranean termites, Coptotermes formosanus Shiraki. However, the mechanisms underlying the induction of termite aggregation by Trichoderma fungi remain unclear. Here, we found that the aqueous or acetone extract of Trichoderma asperellum Samuels, Lieckfeldt & Nirenberg and Trichoderma virens Pers. ex Fries isolated from the gut or cuticle of C. formosanus elicited significant termite aggregation in 2-choice tests. We then screened 9 Trichoderma metabolites (3-acetoxy-2-butanone, phenol, 3-ethoxypropionic acid, ethyl 2,4-dioxovalerate, diglycolic acid, d-valine, styrene, 3-aminopyridine, and hexyl acetoacetate) that triggered termite aggregation. Among them, phenol (1 000 μg/mL), 3-ethoxypropionic acid (10 μg/mL), ethyl 2,4-dioxovalerate (1 000 μg/mL), and diglycolic acid (1 000 μg/mL) showed the strongest activities, triggering termite aggregation throughout the 24-h period. As T. asperellum and T. virens produce different metabolites that trigger aggregation behavior in termites, the mechanisms underlying the interaction between subterranean termites and Trichoderma fungi likely vary. Future studies are needed to test whether these chemicals can attract termites and increase bait consumption.

Exuviae Recycling Can Enhance Queen Oviposition and Colony Growth in Subterranean Termites (Blattodea: Rhinotermitidae: Coptotermes)

Wood-feeding termites have a nitrogen-poor diet and have therefore evolved nitrogen conservation strategies. However, termite workers molt periodically, and throughout the lifetime of a colony, millions of exuviae, a nitrogen-rich resource, are produced by the colony. In Coptotermes Wasmann, workers foraging at remote feeding sites must return to the central part of the nest to molt, where the queen, king, eggs, and larvae are located. It was hypothesized that this molting-site fidelity is an efficient way to recycle nitrogen for reproduction and colony growth, as nestmates involved in exuviae consumption can directly transfer such resources to individuals engaged in reproduction (the queen) or growth (larvae). This study investigates whether incipient colonies of C. gestroi (Wasmann) can gain additional biomass when they are fed supplementary exuviae. Incipient colonies were reared in nitrogen-poor or nitrogen-rich conditions, and 0, 1, 5, or 10 exuviae were added to 3-month-old colonies. After 6.5 months, colonies reared in nitrogen-poor environments gained significantly more biomass when exuviae were added than colonies with no added exuviae. However, the addition of exuviae had no effect on colony growth for colonies reared in nitrogen-rich environments. In a second experiment, queens from colonies in which exuviae were effectively removed laid fewer eggs than queens from colonies in which exuviae were not removed. Therefore, consumption of exuviae from molting individuals by nestmates is an important part of the nitrogen recycling strategy in Coptotermes colonies, as it facilitates queen oviposition and colony growth, especially when such colonies have limited access to nitrogen-rich soils.

Consistency of Cuticular Hydrocarbon Mixtures of Five Reticulitermes (Blattodea: Rhinotermitidae) Taxa From Northern California: Similarity Among Colonies and Seasonal Variation

Cuticular hydrocarbon (CHC) mixtures from workers of five distinct CHC phenotypes of Reticulitermes Holmgren 1913 from two locations in northern California were examined from monthly collections taken over a 3-yr period. The objectives of this study were (1) to identify and quantify variations of the CHCs of multiple colonies of each of these phenotypes (= species or subspecies) to demonstrate consistency, (2) to assess the potential of CHC mixtures to separate or identify colonies within each phenotype, and (3) to detect any temporal changes in each of the hydrocarbons in the CHC mixtures. Nonmetric multidimensional scaling of all CHC mixtures of all samples collected at both locations separated the samples into five clearly visible, different groups of CHC phenotypes (taxa or species) of Reticulitermes. The degree of variability of the CHC mixtures among colonies of each phenotype was such that nonmetric multidimensional scaling did not separate or identify colonies. Strong seasonal fluctuations were evident in some of the CHCs of all five phenotypes and were significantly consistent with a sine curve. Maximum proportions of seasonal CHCs within a phenotype occurred in all seasons of the year but occurred mostly in the winter and summer. In general, the CHCs displaying maximum values in the winter were short-chained (C23-C27) methyl-branched alkanes, whereas the CHCs displaying maximum values in the summer were long-chained (C35-C43) methyl-branched alkanes, which likely influences water retention. These consistent chemical fingerprints are probably responsible for inter-phenotype recognition patterns and are thus useful for chemical taxonomy.

Nationwide Termite Pest Survey Conducted in Taiwan as a Citizen Science Project

Information regarding the species composition and dispersal flight season of termites is crucial for termite management. The major obstacles to collecting such information are a lack of access to private buildings and shortage of workers to monitor and report on termite swarming. To overcome these difficulties, we launched a citizen science project in which members of the public and pest management professionals were invited to collect termite samples. We created the website, Taiwan Termite Identification Service, on which populace could log the collection information, and ship termite samples to our laboratory for identification. We also established a Facebook group, called the "Termite Forum," to publicize this project. A total of 3024 samples were collected from 2015 to 2020, and we identified the species of >93% of the samples. Based on 1499 samples collected from buildings, five structural termite pests were identified, and species composition in each county of Taiwan is available. According to 844 dispersal flight events, termite dispersal flight timing peak and degree of centralization were estimated using a Gaussian model. The collected data demonstrated that the invasive termite species, Coptotermes gestroi (Wasmann) (Blattodea: Rhinotermitidae), continued northward expansion. The first intercepted alate of Schedorhinotermes sp. (Blattodea: Rhinotermitidae) indicated that it may be a new invasive pest from Southeast Asia. This study reports on a successful case of a citizen science project where urban pest data were collected on a national scale.

Toxicological, Behavioral, and Horizontal Transfer Effects of Cycloxaprid Against Formosan Subterranean Termites (Blattodea: Rhinotermitidae)

Cycloxaprid, 9-((6-chloropyrid-3-yl)methyl)-4-nitro-8-oxa-10,11-dihydroimidazo-[2,3-a]-bicyclo-[3,2,1]-oct-3-ene, is a cis-configuration neonicotinoid insecticide. In the present study, the lethal and sublethal effect of cycloxaprid against Formosan subterranean termites, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), was evaluated and compared with fipronil. Toxicity bioassays showed that cycloxaprid had slightly lower toxicity than fipronil. The minimum cycloxaprid concentration in sand and soil that causes 100% termite mortality was 100 ppm. Similar to fipronil, cycloxaprid significantly reduced wood consumption and tunneling activities of termites. In the tunneling-choice tests, termite tunneling activity measured in both length and area was significantly lower in sand treated with cycloxaprid (10 or 100 ppm) than that in untreated sand. In the aggregation-choice tests, cycloxaprid exhibited inhibition to termite aggregation starting from 100 ppm. In addition, cycloxaprid exhibited significant horizontal transfer effect at 10 ppm. In conclusion, our study showed that cycloxaprid is slightly less toxic than fipronil and more repellent to C. formosanus than fipronil. Future studies are needed to evaluate the effectiveness of cycloxaprid against subterranean termites in the field.

Efficacy of Minimum Application of Chlorfluazuron Baiting to Control Urban Subterranean Termite Populations of Coptotermes gestroi (Wasmann) (Blattodea: Rhinotermitidae)

Simple Summary

The termite baiting system has emerged as a popular option for controlling subterranean termites. The effectiveness of termite baiting depends on the foraging of the termites to encounter the bait, feed on the bait, and the horizontal transfer of residual insecticide deposits between nestmates. However, termite baiting can be costly and time consuming. Thus, this study looks to minimize the termite baiting application which leads to the total colony elimination. Overall, this study found that a termite colony population can be eliminated by selective termite baiting treatment.

Abstract

Termite infestations in urban areas are a serious problem because they cause negative economic effects, reduce the esthetic value of buildings, damage crops, and require household repairs. Chemical controls are the most common method used against subterranean termites, and baiting has emerged as one of the prominent control methods. The goal of this research was to determine the efficacy of termite baiting by treating one of six active termite stations (selective baiting) with chlorfluazuron baits to eradicate six populations of subterranean termites. This work shows that the placement of chlorfluazuron baits in one of the active stations was sufficient to destroy a colony that was interconnected with multiple chlorfluazuron-free stations. In general, it requires an average of 4–8 weeks for a quantity of less than 300 g of chlorfluazuron bait to remove a termite infestation at the study site.

A Comparison of Morphology among Four Termite Species with Different Moisture Requirements

The thicknesses of the cuticle and rectal pads, and the spiracle morphology were compared for four termite species from different habitats, including one drywood termite, Cryptotermes brevis Walker, one “wetwood” termite, Cryptotermes cavifrons Banks, one subterranean termite, Coptotermes formosanus Shiraki, and one dampwood termite, Neotermes jouteli (Banks). Cuticle thicknesses were significantly different among all four termite species. Neotermes jouteli had the thickest cuticle, while Co. formosanus had the thinnest. The cuticle of C. brevis was thicker than that of C. cavifrons and Co. formosanus, which may reflect a comparably greater need to prevent water loss in drier habitats for C. brevis. Rectal pad widths were significantly different among all four termite species, except those of C. brevis with N. jouteli. The rectal pads of N. jouteli and C. brevis were thicker than those of C. cavifrons and Co. formosanus, and the rectal pads of C. cavifrons were thicker than those of Co. formosanus in turn. Larger rectal pads likely account for the water conservation mechanism of producing dry, pelleted frass in the kalotermitids (N. jouteli, C. brevis, and C. cavifrons). Morphological observations of the spiracles showed the presence of protuberances (atrial arms) in the three kalotermitids. The function of this protuberance is unclear, but it may serve as a sac-like structure, aiding in gas exchange, or a moisture trap aiding in the prevention of water loss through evaporation.

Identification of Subterranean Termite Genus, Reticulitermes (Blattodea: Rhinotermitidae) in Taiwan

Species identification in the genus Reticulitermes is often difficult because of ambiguous morphological characters. Challenges in Reticulitermes spp. recognition have also been encountered in East Asia, including Taiwan. Because of unknown Reticulitermes taxa in Taiwan and the possible origin of alien Reticulitermes kanmonensis Takematsu in Japan and Korea, reexamining Reticulitermes fauna in Taiwan is imperative. To clarify the Reticulitermes fauna in Taiwan, this study applied two mitochondrial genes (cytochrome oxidase subunit II [COII] and 16S rDNA) and morphological characters for species delimitation. Reticulitermes specimens collected from 63 localities across the main and adjacent islands of Taiwan were analyzed. Phylogenetic analyses, morphological comparisons, and ecological traits suggested the existence of three species in Taiwan: Reticulitermes flaviceps (Oshima), R. kanmonensis, and Reticulitermes leptomandibularis Hsia and Fan. Altitudinal distributions among the three Reticulitermes termites tended to differ: R. flaviceps adapted to low hills, but R. kanmonensis and R. leptomandibularis occurred in medium mountainous areas. The combined data, including haplotype diversities and distribution range, suggest that 1) R. flaviceps is an endemic species and only found in Taiwan; 2) R. kanmonensis and R. leptomandibularis are both native species in Taiwan and China; 3) Japanese R. kanmonensis populations originated from southern China and/or Taiwan and that Korean populations were possibly introduced from Japan.

Cuticular Permeability, Percent Body Water Loss, and Relative Humidity Equilibria Comparisons of Four Termite Species

This study compared percentage of total body water (%TBW), water loss rate under desiccative conditions, and cuticular permeability (CP) of four termite species (Order: Blattodea, Infraorder: Isoptera) from different habitats, including one subterranean termite, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), one dampwood termite, Neotermes jouteli (Banks) (Blattodea: Kalotermitidae), one 'wetwood' termite, Cryptotermes cavifrons Banks (Blattodea: Kalotermitidae), and one drywood termite, Cryptotermes brevis Walker (Blattodea: Kalotermitidae). There was no consistent pattern associated with the habitat relative humidity (RH) levels and the %TBW among the four termite species tested. Because C. formosanus forage for food, its lowest %TBW may be due to its ability to access water sources, and its need to be more mobile than kalotermitids that remain in wood. Body water loss rate and CP were lower for xeric species such as Cr. brevis than hydric species such as N. jouteli. An RH equilibrium represents the capacity of termite water retention mechanisms that may include the physical structure of cuticular layers, behavioral manipulation of natural openings, and physiological means. As with water loss rate and CP data, RH equilibria were lower for xeric species such as Cr. brevis than hydric species such as N. jouteli. Moreover, RH equilibria for dead individuals of the four termite species were significantly higher than those of live individuals, indicating dead termites lost more water after losing their physiological and behavioral means of retaining water. RH equilibria represent termites' capability in water retention, and there is a strong linear relationship between RH equilibria and CP values. Hence, RH equilibria may offer simpler alternatives to CP estimates.

Symbiotic flagellate protists as cryptic drivers of adaptation and invasiveness of the subterranean termite Reticulitermes grassei Clément

Changes in flagellate protist communities of subterranean termite Reticulitermes grassei across different locations were evaluated following four predictions: (i) Rural endemic (Portugal mainland) termite populations will exhibit high diversity of symbionts; (ii) invasive urban populations (Horta city, Faial island, Azores), on the contrary, will exhibit lower diversity of symbionts, showing high similarity of symbiont assemblages through environmental filtering; (iii) recent historical colonization of isolated regions-as the case of islands-will imply a loss of symbiont diversity; and (iv) island isolation will trigger a change in colony breeding structure toward a less aggressive behavior. Symbiont flagellate protist communities were morphologically identified, and species richness and relative abundances, as well as biodiversity indices, were used to compare symbiotic communities in colonies from urban and rural environments and between island invasive and mainland endemic populations. To evaluate prediction on the impact of isolation (iv), aggression tests were performed among termites comprising island invasive and mainland endemic populations. A core group of flagellates and secondary facultative symbionts was identified. Termites from rural environments showed, in the majority of observed colonies, more diverse and abundant protist communities, probably confirming prediction (i). Corroborating prediction (ii), the two least diverse communities belong to termites captured inside urban areas. The Azorean invasive termite colonies had more diverse protist communities than expected and prediction (iii) which was not verified within this study. Termites from mainland populations showed a high level of aggressiveness between neighboring colonies, in contrast to the invasive colonies from Horta city, which were not aggressive to neighbors according to prediction (iv). The symbiotic flagellate community of R. grassei showed the ability to change in a way that might be consistent with adaptation to available conditions, possibly contributing to optimization of the colonization of new habitats and spreading of its distribution area, highlighting R. grassei potential as an invasive species.

Flight Phenology of Two Coptotermes Species (Isoptera: Rhinotermitidae) in Southeastern Florida

The dispersal flight activity ("swarming") of two invasive subterranean termite species, Coptotermes gestroi (Wasmann) and Coptotermes formosanus Shiraki, was monitored in metropolitan southeastern Florida, where both species are now sympatric and major structural pests. Historical records of alates collected in the area showed that the two species have distinct peaks of flight activity, from mid-February to late April for C. gestroi, and from early April to late June for C. formosanus. However, an overlap of the two dispersal flight seasons has been observed since at least 2005. The daily monitoring of dispersal flight events in southeastern Florida in 2014, 2015, and 2016 confirmed that simultaneous flights occurred several times each year. In addition, environmental conditions for favorable flights were identified, and it was established that low temperature was the primary factor inhibiting both species from dispersal flights, while all other factors had little impact on the occurrence of major dispersal flight events. However, both species shared similar temperature requirements for favorable dispersal flight conditions despite distinct peaks of activity over time. The analysis of sex ratios and average weights of the alates suggests that intrinsic colony factors are important for the timing of the maturation of alates, and that once a cohort of individuals is ready to disperse, a flight may occur as soon as the environmental conditions are favorable.

Subterranean Termite Resistance of Polystyrene-Treated Wood from Three Tropical Wood Species

The objective of this work was to investigate the resistance of three Indonesian wood species to termite attack. Samples from sengon (Falcataria moluccana), mangium (Acacia mangium), and pine (Pinus merkusii) were treated with polystyrene at loading levels of 26.0%, 8.6%, and 7.7%, respectively. Treated and untreated samples were exposed to environmental conditions in the field for 3 months. Untreated specimens of sengon, mangium, and pine had resistance ratings of 3.0, 4.6, and 2.4, respectively, based on a 10-point scale from 0 (no resistance) to 10 (complete or near-complete resistance). Corresponding resistance values of 7.8, 7.2, and 8.2 were determined for specimens treated with polystyrene. Overall weight loss values of 50.3%, 23.3%, and 66.4% were found for untreated sengon, mangium, and pine samples, respectively; for treated samples, the values were 7.6%, 14.4%, and 5.1%, respectively. Based on the findings in this study, overall resistance to termite attack was higher for treated samples compared to untreated samples.

Naturalization and Control of Coptotermes gestroi (Blattodea: Rhinotermitidae) in a Taiwanese Forest

Coptotermes gestroi (Wasmann), an invasive termite species in Taiwan, has been a major structural pest in southwestern Taiwan. C. gestroi was recently reported to have infested living trees in a Taiwanese forest, showing its potential of becoming an invasive forest pest in Taiwan. To determine whether C. gestroi have naturalized in the forests, we monitored their dispersal flights and estimated their colony development status on the basis of their worker and soldier morphology. The results showed that mature C. gestroi colonies occurred in forest, indicating that C. gestroi has naturalized. The colony sizes of C. gestroi were estimated using a triple mark-release-recapture method. The three studied colonies contained 0.12-0.20 million individuals, which was smaller than that reported in previous studies conducted in urban environments. We speculate that C. gestroi population is suppressed by ants and another dominant termite species, Odontotermes formosanus (Shiraki). Colony elimination was achieved four months after employing termite baits for controlling the three colonies of C. gestroi in forest. In summary, although C. gestroi have naturalized in Taiwan, their further expansion in the forest has likely been restricted by ants and other termite species. Termite baits can be a practical option for controlling C. gestroi in the forests.

Impacts on Reticulitermes flavipes (Infraorder Isoptera: Rhinotermitidae) by Chlorantraniliprole Applied to Soil Surrounding Established Tunnels

Soil-applied liquid termiticides are the most common control measure for subterranean termites. Characteristics unique to insecticidal chemistries such as repellency, toxicity, and time between contact and mortality, influence the interaction of termites with treated soil and overall treatment success. Two different treated-tunnel bioassays were used to evaluate the behavioral impacts and mortality of termites from treatment with chlorantraniliprole (the active ingredient in Altriset® termiticide) to existing, mature tunnels. Termites that were provided constant access to a 10-cm-long mature tunnel within soil treated with 5 or 50 ppm chlorantraniliprole were not repelled by the treatment and began exhibiting slower, uncoordinated movement, and cessation of tunneling and feeding in as little as 1 h after access. Termites provided access for 7, 14, or 21 d to previously constructed tunnels recently treated with 50 ppm chlorantraniliprole exhibited complete or near complete mortality by 28 d. The second bioassay design resembled a more typical field situation with a 40-cm-long mature tunnel and termites allowed access for a maximum of 5 min. Termites collected after just 5 min of access to the previously constructed tunnels recently treated with 50 ppm chlorantraniliprole exhibited similar symptomology within an hour followed by complete mortality at 18 d after exposure. These test designs simulate what occurs in the soil around an infested structure at the time of treatment. Results from these evaluations suggest that termites readily crawl through chlorantraniliprole-treated mature tunnels, rapidly lose ability to feed, and acquire a lethal dose from brief exposures.

and Coptotermes formosanus [Isoptera: Rhinotermitidae]) on Structures

A field study was initiated in 2009 with 0.5% novaluron the BASF Advance Termite Bait System, which was 100% effective in controlling Reticulitermes sp. Holmgren and Coptotermes formosanus Shiraki infestations on 11 structures in the Texas City, TX area. Stations with inspection cartridges (cellulose tablets) and monitoring bases (southern yellow pine) and independent monitoring devices were installed in an alternating pattern around each structure and were inspected every 30 d postinstallation. When subterranean termite activity was confirmed on the inspection cartridge or the monitoring base, the inspection cartridge was removed and replaced with a bait cartridge containing 0.5% novaluron insecticide on a proprietary matrix (124 g/cartridge) in a station. Once the novaluron-treated bait was inserted, inspections of that station were made on a 4-mo cycle until no termite activity was observed. The mean time to achieve control of the subterranean termites on the structures was 10.5 mo post initial installation of bait. Mean time to achieve control of the termites on the structures after the baits were installed was 5.4 mo. Control of the termites on the structures required consumption of a mean of 1.3 bait cartridges (166.2 g) of 0.5% novaluron bait matrix per structure. These results indicate that the baits with 0.5% novaluron were effective in controlling termites on the structures used in this study.

Sodium Fluoride for Protection of Wood Against Field Populations of Subterranean Termites

Sodium fluoride (NaF) is a wood preservative with fungicidal activity and antifeedant activity against termites. In this study, wood blocks of Pinus massoniana were treated with a 0.5% (wt/wt) aqueous solution of NaF, and placed in soil contact under field conditions to evaluate leachability of NaF and resistance to Reticulitermes flaviceps (Oshima). Fluoride leachate levels in soil from wood-soil locations were also determined. After 12-mo outdoor exposure, 91.54% of fluoride was leached from NaF-treated wood and fluoride retention of the wood was 154.28 μg/g wood. In NaF-treated wood-soil locations, soil fluoride residues were significantly higher than locations with the water-treated negative control. Termite activity (presence or occupation) on NaF-treated blocks was 6.25% which was significantly less than 40.00% activity on water-treated control blocks. The mass lost from the wood of NaF-treated blocks was 17.46% which was significantly less than the 45.21% loss from the water-treated blocks. The results show that fluoride is readily leachable from treated wood into surrounding soil. NaF treatment can reduce termite damage to wood under field conditions, and this compound should receive further consideration as a wood preservative to protect timber from termite damage.

Resistance of Particleboards Made from Fast-Growing Wood Species to Subterranean Termite Attack

Laboratory-made particleboards were tested for their resistance to subterranean termite, Coptotermes curvignathus Holmgren (Order Isoptera, Family Termitidae) by Indonesian standard SNI 01.7207–2006, during four weeks and at the end of the test their mass loss percentage and feeding rate were determined. Particleboards consisted of: jabon (Anthocephalus cadamba, Family Rubiacea) with a density of 0.41 g/cm³; sungkai (Peronema canescens, Family Verbenaceae) with a density of 0.46 g/cm³; mangium (Acacia mangium, Family Rhamnaceae) with a density of 0.60 g/cm³ separately and the three species mixture at a rate of 1:1:1. Densities of the boards were targetted at 0.60 g/cm³ and 0.80 g/cm³ by using 12% urea formaldehyde as binder with 2% paraffin as additive based on oven dry wood particle weight. The hand-formed mats and hot-pressing at 130 °C and 2.45 MPa for 10 min were applied. The results showed that particleboards density did not affect mass loss and feeding rate, but the particleboards made from higher density wood resulted in higher resistance to subterranean termite attack. The most resistant particleboards were made of magium, followed by sungkai, mixed species, and jabon.

Individual Behavior of Workers of the Formosan Subterranean Termite (Isoptera: Rhinotermitidae) on Consecutive Days of Tunnel Construction

This study examines the individual behavior of workers of the Formosan subterranean termite, Coptotermes formosanus Shirkai, on two consecutive days of tunnel construction. In each trial, a group of 30 termite workers was observed continuously during the first 60 min of construction of a new tunnel on two consecutive days. On each day, an average of 68% of individuals did not participate in tunnel construction, 19% spent <25 min tunneling, and 13% spent ≥25 min tunneling. There were specific individuals that did most of the work in the construction of new tunnels on both days. An individual that spent at least 25 min tunneling on Day 1 was significantly more likely to spend at least 25 min tunneling on Day 2 than individuals that spent <25 min tunneling on Day 1. When individuals were ranked based on the time spent tunneling on Day 1 and Day 2, there were individuals ranked as one of the top four excavators on both days in three of the four groups. These results indicate that there is evidence of task allocation by termite workers during the construction of a new tunnel.

A constraint condition for foraging strategy in subterranean termites

Previous studies have explored the relationship between termite branch tunnel geometry and foraging efficiency in a model simulation in which foraging efficiency, γ, for two termite species, Coptotermes formosanus Shiraki and Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae), was investigated in response to two variables, the probability of tunnel branching (P(branch)) and the probability of tunnel branch termination (Pterm). It was found that simulated tunnel patterns based on empirical data did not have maximum foraging efficiency. We hypothesized that termites could increase their foraging efficiency in response to landscape heterogeneity. The present study investigated how termites could control the two variables, P(branch) and P(term), in response to the external environment in terms of tunnel network connectivity. It was found that the best simulated strategy for C. formosanus and R. flavipes termites would occur if both P(branch) and P(term) were increased together. This study provides possible mechanisms for foraging strategies in subterranean termites and a baseline for future empirical work.