Trophic Path of Marked Exuviae Within Colonies of Coptotermes gestroi (Blattodea: Rhinotermitidae).

Nitrogen, a limiting growth factor in wood-feeding insects, was hypothesized to play a role in the recently discovered behavior of subterranean termites returning to the nest to molt. Coptotermes gestroi (Wasmann) exuviae is approximately 11% N by dry weight, and therefore a potentially rich source of recyclable nitrogen. Exuviae from a C. gestroi colony were marked with immunoglobulin G (IgG) and were fed to two-year-old C. gestroi colonies. IgG-marked exuviae were detected with an enzyme-linked immunosorbent assay. The IgG marker was later detected in every caste and life stage except first-instar larvae (L1). The proportion of individuals positive for the marker varied by caste, with the queens always being positive for the marker. The queens and second-or-higher-instar workers (W2+) had significantly higher concentrations of the marker than the eggs and L1. The trophic path of exuviae includes individuals that directly fed on marked exuviae (workers and possibly second-instar larvae) and individuals that secondarily received marked exuviae through trophallaxis (queens, kings, and soldiers). This study described the trophic path of consumed exuviae and demonstrated its role in the recycling of nitrogen in a subterranean termite. Molting at the central nest may be an efficient means to transfer nitrogen from shed exuviae to recipients and may be a nitrogen recycling behavior conserved from a termite ancestor.

Soldier phenotypic differences among 2 invasive and destructive Coptotermes species and their hybrids (Blattodea: Isoptera: Rhinotermitidae).

With recent evidence of hybridization events in the field, the phenotypic traits of F1 hybrid colonies of 2 destructive subterranean termite species, Coptotermes formosanus Shiraki and Coptotermes gestroi (Wasmann) remain to be investigated. In this study, laboratory colonies of 2 conspecific pairings and 2 heterospecific pairings (hybrid F = ♀C. formosanus × ♂C. gestroi, hybrid G = ♀C. gestroi × ♂C. formosanus) were examined in Florida, USA, and in Taiwan. Colony nest architecture for both hybrids displayed disorganized carton materials compared to the defined trabecular carton of both parental species. Soldier head measurements were not a reliable approach for diagnostic purposes, as soldier morphometric traits widely overlapped across all mating combinations, except for hybrid F soldiers displaying abnormally long mandibles. Hybrid F soldiers' mandibles also remained parallel when at rest. However, 4 qualitative morphological differences in soldiers were determined for diagnostic purposes. First, the fontanelle in both hybrids is horizontally ellipsoid whereas subcircular in C. gestroi and trianguliform in C. formosanus. Second, sclerotized striations along the postmental sulcus are present in C. gestroi, absent in C. formosanus, and intermediate in both hybrid soldier types. Third, each lateral margin of the fontanelle is flanked by 2 setae in C. formosanus and both hybrids, while a single seta resides on each side of the fontanelle in C. gestroi. Finally, C. gestroi and hybrid soldiers' heads are characterized by a bulging vertex that is lacking in C. formosanus. Therefore, a combination of these 4 characteristics now allows for soldier identification of hybrid Coptotermes.

Differential time allocation of foraging workers in the subterranean termite.

BACKGROUND: Foraging in group living animals such as social insects, is collectively performed by individuals. However, our understanding on foraging behavior of subterranean termites is extremely limited, as the process of foraging in the field is mostly concealed. Because of this limitation, foraging behaviors of subterranean termites were indirectly investigated in the laboratory through tunnel geometry analysis and observations on tunneling behaviors. In this study, we tracked subsets of foraging workers from juvenile colonies of Coptotermes formosanus (2-yr-old) to describe general foraging behavioral sequences and to find how foraging workers allocate time between the foraging site (food acquisition or processing) and non-foraging site (food transportation). RESULTS: Once workers entered into the foraging site, they spent, on average, a significantly longer time at the foraging site than the non-foraging site. Our clustering analysis revealed two different types of foraging workers in the subterranean termite based on the duration of time they spent at the foraging site and their foraging frequency. After entering the foraging site, some workers (cluster 1) immediately initiated masticating wood fragments, which they transferred as food boluses to recipient workers at the foraging site. Conversely, the recipient workers (cluster 2) moved around after entering the foraging site and received food from donating workers. CONCLUSIONS: This study provides evidence of task specialization within foraging cohorts in subterranean termites.

The Complete Protist Symbiont Communities of Coptotermes formosanus and Coptotermes gestroi: Morphological and Molecular Characterization of Five New Species.

Coptotermes formosanus Shiraki and Coptotermes gestroi (Wasmann) (Blattoidea: Rhinotermitidae) are invasive subterranean termite pest species with a major global economic impact. However, the descriptions of the mutualistic protist communities harbored in their respective hindguts remain fragmentary. The C. formosanus hindgut has long been considered to harbor three protist species, Pseudotrichonympha grassii (Trichonymphida), Holomastigotoides hartmanni, and Cononympha (Spirotrichonympha) leidyi (Spirotrichonymphida), but molecular data have suggested that the diversity may be higher. Meanwhile, the C. gestroi community remains undescribed except for Pseudotrichonympha leei. To complete the characterization of these communities, hindguts of workers from both termite species were investigated using single-cell PCR, microscopy, cell counts, and 18S rRNA amplicon sequencing. The two hosts were found to harbor intriguingly parallel protist communities, each consisting of one Pseudotrichonympha species, two Holomastigotoides species, and two Cononympha species. All protist species were unique to their respective hosts, which last shared a common ancestor ~18 MYA. The relative abundances of protist species in each hindgut differed remarkably between cell count data and 18S rRNA profiles, calling for caution in interpreting species abundances from amplicon data. This study will enable future research in C. formosanus and C. gestroi hybrids, which provide a unique opportunity to study protist community inheritance, compatibility, and potential contribution to hybrid vigor.

Development of Baits for Population Management of Subterranean Termites.

The objective of bait application envisioned by early researchers was to eliminate the source of infestation, the colony, but because of the lack of adequate evaluation tools, results of field trials with mirex baits in the 1960s were mostly inconclusive. On-the-ground monitoring stations and mark-recapture protocol developed in the 1970s marked the turning point in the field studies of termite baits. Results of field studies with metabolic inhibitors and chitin synthesis inhibitors (CSIs) in the 1990s indicated that a bait toxicant has to be slow-acting and nonrepellent, and its lethal time has to be dose independent. A recent discovery that termites return to the central nest to molt and CSI-poisoned termites die near the royal pair further explains the success of CSI baits in eliminating colonies. Owing to the availability of durable baits that require less-frequent site inspection, more termite control professionals have adopted baiting systems in recent years.

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.

Chemical Interaction among Termite-Associated Microbes.

Bacteria and fungi in shared environments compete with one another for common substrates, and this competition typically involves microbially-produced small molecules. An investigation of one shared environmental niche, the carton material of the Formosan subterranean termite Coptotermes formosanus, identified the participants on one of these molecular exchanges. Molecular characterization of several termite-associated actinobacteria strains identified eleven known antimicrobial metabolites that may aid in protecting the C. formosanus colony from pathogenic fungal infections. One particular actinobacterial-derived small molecule, bafilomycin C1, elicited a strong chemical response from Trichoderma harzianum, a common soil saprophyte. Upon purification and structure elucidation, three major fungal metabolites were identified, t22-azaphilone, cryptenol, and homodimericin A. Both t22-azaphilone and homodimericin A are strongly upregulated, 123- and 38-fold, respectively, when exposed to bafilomycin C1, suggesting each play a role in defending T. harzianum from the toxic effect of bafilomycin C1.

Reinvasion Dynamics of Subterranean Termites (Isoptera: Rhinotermitidae) Following the Elimination of All Detectable Colonies in a Large Area.

Following the elimination of all detectable termite colonies in the 32-acre Louis Armstrong Park in New Orleans, LA, in 2002­2003, termite activity was monitored by using 808 Sentricon stations. Between January 2004 and July 2005, termites were found in 8­11 stations. In August 2005, the Park was flooded by Hurricane Katrina, but termites remained active. Post-Katrina termite activity levels of 16­21 stations were recorded throughout 2006, and in October 2007, the activity drastically increased to 43 stations. This rapid increase of termite activity continued into 2008, and a total of 94 stations harbored termite activities by July 2008. Termite activity peaked at 109 stations in September 2008 and then leveled down to 64 stations in March 2009. Termite activity in the Park between 2004 and 2009 was described by a Sigmoid model with a carrying capacity of 76 stations, and a Sigmoid mid-point of 1,202 d. In April 2009, a total of 14 colonies of Coptotermes formosanus Shiraki and one colony of Reticulitermes flavipes (Kollar) were delineated by using microsatellite genotyping and mark­recapture protocol. Of the 15 colonies, eight near the Park border probably originated from existing colonies from outside, and seven C. formosanus colonies found inside the Park were probably initiated by alate pairs. Our results showed that, if surrounded by high population pressure of termites and no control measures are applied, an area cleared of termite populations by baits can be completely re-populated by termites from outside in 53 mo.

Postecdysis Sclerotization of Mouthparts of the Formosan Subterranean Termites (Isoptera: Rhinotermitidae).

In termites, it is challenging to recognize the incidence of molting in workers because of their successive stationary molt, asynchronous molting among individuals, cryptic behavior, a soft and poorly sclerotized cuticle, and they immediately consume the shed exuvia of nestmates. This study describes a method in which the degree of sclerotization of the mouthparts in newly molted workers of the Formosan subterranean termite can be quantified and used to determine if an individual has recently molted, within a 36-h time frame. Changes in the tanning of mouthparts over time were used as a measure of the index of sclerotization in workers postmolting. Upon ecdysis, the primary point of articulation of the mandible already initiated sclerotization, which may allow the movement of the mandibles during the shedding of the exuvium. The sclerotization of the secondary point of articulation and the mandibular teeth, and the width of sclerotization of the mandibles, progressively increased until reaching a plateau around 36-h postecdysis, which imply that workers can regain some level of activity as early as 2 d after ecdysis. Our observations allowed for the determination of variables for the sclerotization of the mouthparts to easily identify workers that recently molted, and this method will be useful in future studies that focus on the molting activity of workers over time and space within a termite colony, in the scope of improving current control strategies for termite pests.

A Fluid Bait for Remedial Control of Subterranean Termites.

A fluid bait, comprising α-cellulose and fine-ground phagostimulants (Summon Preferred Food Source) impregnated with 0.5% hexaflumuron (AI wt/wt) and mixed with 1% methylcel solution to yield 10% dry weight, was injected into simulated foraging galleries of Coptotermes formosanus Shiraki and Reticulitermes virginicus (Banks) for a laboratory efficacy evaluation. Six weeks after the injection, mortalities for both species exceeded 90%, and all termites died by the eight wk. The fluid bait can be applied internally through a small drill hole in a tight spot with any surface contour and may bypass many problems associated with the AG system that has to be installed externally on the walls or wood surface. When injected into an active gallery of termites in a structure, a tree, or in soil, the fluid baits may be fed immediately by termites to achieve the colony elimination.

Dispersal Flights of the Formosan Subterranean Termite (Isoptera: Rhinotermitidae).

The Formosan subterranean termite, Coptotermes formosanus Shiraki, is a pest of major economic concern. This termite is particularly known for its tendency to establish populations in nonendemic areas via maritime vessels as well as human-aided transport of infested materials. The natural spread of this species after new introductions occurs in part by dispersal flights originating from mature colonies. Dispersal flight activity is also the primary variable for the evaluation of area-wide management programs. Few studies exist describing the dynamics and distribution of a typical dispersal flight for this species. The present study used data collected by mark-recapture of C. formosanus alates over 12 individual evenings of dispersal flights in the New Orleans French Quarter. In this study, we found that for one selected flight dispersal location, which was not affected by a high density of trap locations nearby, alates flew on average 621 m from their parent colony. A new record of a 1,300-m dispersal flight was recorded. Spatial analysis showed that neither wind nor light affected the direction of flight, which may, however, be attributed to scarce light and wind measurements in the study region.

Behavioral and histological changes in the Formosan subterranean termite (Isoptera: Rhinotermitidae) induced by the chitin synthesis inhibitor noviflumuron.

This study describes the behavioral and histological changes of the molting process in Coptotermes formosanus Shiraki caused by the chitin synthesis inhibitor noviflumuron. Termites exposed to noviflumuron initiated ecdysis as untreated individuals did; however, peristalsis contractions were weak and the expansion of the dorsal breach of the exoskeleton did not occur. Treated termites could not complete their molting process and died after the initiation of the ecdysis. Histological observations showed that the process of voiding the gut protozoa during premolting was not affected by the noviflumuron treatment. However, the formation of the new cuticle was disrupted resulting in the loss of integrity of the cuticle. The alteration of the cuticle was visible in the gizzard (foregut), the thoracic pleurons, and most of the exoskeleton. Muscles were partially able to reattach to the incompletely formed new cuticle, and muscle contractions resulted in tearing off the cuticle. Because the integrity of the newly formed cuticle was compromised by the noviflumuron treatment, we concluded that termites' death was caused primarily by the loss of hemolymph as a result of the damage done by the muscle contractions on the exoskeleton during the peristalsis. As the physiological homeostasis was disrupted, termites were too weak to shed their old cuticle, ultimately resulting in termite dying during the molting process.

Feeding cessation after feeding on 20-hydroxyecdysone in the Formosan subterranean termite.

BACKGROUND: To control subterranean termite pests, chitin synthesis inhibitor (CSI) baits have been widely applied. Despite CSI baits having low impacts on the environment, they require a lengthy time period to eliminate colonies. 20-hydroxyecdysone (20E) was proposed to speed up the baiting process as it showed faster mortality than CSI baits. However, the efficacy of 20E has previously not been tested at the colony level prior to applying in the field. RESULTS: We compared the effect of 20E, 20E + noviflumuron, noviflumuron and untreated control using colonies of Coptotermes formosanus. Our result revealed that both 20E and 20E + noviflumuron did not accelerate colony elimination and termite activity remained relatively stable during the observation periods. To determine the limited effects of 20E, we further investigated feeding duration and consumption amount of 20E with different concentrations (control, 100 and 1000 ppm) for 10 days. Termites ceased feeding after 1 day in 100 and 1000 ppm treatment and 100% mortality was observed within 10 days in 1000 ppm 20E, while mortality in the 100 ppm 20E treated group was much lower than that in the 1000 ppm group. Furthermore, no termites molted in the control and termites died from hyperecdysonism in 1000 ppm 20E treatment, whereas about 20% of termites molted in 100 ppm 20E. CONCLUSION: This study demonstrated that 20E may not be suitable as a sole active ingredient to accelerate elimination of a subterranean termite colony, while CSI baits and lower concentrations of 20E may reduce the lengthy time period in colony elimination. © 2023 Society of Chemical Industry.

Genomic data provide insights into the classification of extant termites.

The higher classification of termites requires substantial revision as the Neoisoptera, the most diverse termite lineage, comprise many paraphyletic and polyphyletic higher taxa. Here, we produce an updated termite classification using genomic-scale analyses. We reconstruct phylogenies under diverse substitution models with ultraconserved elements analyzed as concatenated matrices or within the multi-species coalescence framework. Our classification is further supported by analyses controlling for rogue loci and taxa, and topological tests. We show that the Neoisoptera are composed of seven family-level monophyletic lineages, including the Heterotermitidae Froggatt, Psammotermitidae Holmgren, and Termitogetonidae Holmgren, raised from subfamilial rank. The species-rich Termitidae are composed of 18 subfamily-level monophyletic lineages, including the new subfamilies Crepititermitinae, Cylindrotermitinae, Forficulitermitinae, Neocapritermitinae, Protohamitermitinae, and Promirotermitinae; and the revived Amitermitinae Kemner, Microcerotermitinae Holmgren, and Mirocapritermitinae Kemner. Building an updated taxonomic classification on the foundation of unambiguously supported monophyletic lineages makes it highly resilient to potential destabilization caused by the future availability of novel phylogenetic markers and methods. The taxonomic stability is further guaranteed by the modularity of the new termite classification, designed to accommodate as-yet undescribed species with uncertain affinities to the herein delimited monophyletic lineages in the form of new families or subfamilies.

Extended disease resistance emerging from the faecal nest of a subterranean termite.

Social insects nesting in soil environments are in constant contact with entomopathogens but have evolved a range of defence mechanisms, resulting in both individual and social immunity that reduce the chance for epizootics in the colony, as in the case of subterranean termites. Coptotermes formosanus uses its faeces as building material for its nest structure that result into a 'carton material', and here, we report that the faecal nest supports the growth of Actinobacteria which provide another level of protection to the social group against entomopathogens. A Streptomyces species with in vivo antimicrobial activity against fungal entomopathogens was isolated from the nest material of multiple termite colonies. Termite groups were exposed to Metarhizium anisopliae, a fungal entomopathogen, during their foraging activity and the presence of Streptomyces within the nest structure provided a significant survival benefit to the termites. Therefore, this report describes a non-nutritional exosymbiosis in a termite, in the form of a defensive mutualism which has emerged from the use of faecal material in the nesting structure of Coptotermes. The association with an Actinobacteria community in the termite faecal material provides an extended disease resistance to the termite group as another level of defence, in addition to their individual and social immunity.

Estimating population size of large laboratory colonies of the Formosan subterranean termite using the capture probability equilibrium.

The reliability of the capture probability equilibrium model developed by Su and Lee (2008) for population estimate was tested in three-directional extended foraging arenas connecting to large Plexiglas cubes (96 by 96 by 96 cm) containing approximately 100,000-400,000 workers of the Formosan subterranean termite, Coptotermes formosanus Shiraki. After the release of marked termites in the arenas, the capture probability was averaged for three directions at equal distance from the release point. The daily data of directionally averaged capture probability were subject to a linear regression with distance as the independent variable to identify the capture probability equilibrium. When the daily data produced significant regressions with regression slope [b] < or = 0.05 or [b] approximately 0.05, the directionally averaged capture probability was considered to have reached equilibrium, and the regression intercept was used in the Lincoln index to derive the population estimate. Of the four laboratory colonies tested, three met the criteria, and the equilibrium models yielded population estimates that were not significantly different from the known numbers of workers in the arenas.

Predicting habitat suitability of Coptotermes gestroi (Isoptera: Rhinotermitidae) with species distribution models.

Coptotermes gestroi (Wasmann) is an important structural pest reported from Asia, Pacific islands, North America, Caribbean islands, South America, and Indian Ocean islands. This study summarized previous records of C. gestroi and its synonyms, presenting 184 infested counties from 24 countries. Based on the geo-references occurrence locations and global raster data of climate, geography, and human population, C. gestroi were found most commonly in warm, high precipitation, low altitude, and human populated areas. By using species distribution models, we predicted its current infested area (model 1), habitat suitability (model 2), and probability of introduction (model 3) on a global scale. The results showed its recorded locations and the predicted distribution of the present day are similar, but the suitable habitat is larger than its current distribution. The patterns of the introduction frequency (model 3) and habitat suitability (model 2) are inconsistent. Temperate cities with high introduction risk are located in Europe, United Sates, northeastern China, and Japan where habitat suitability is low and hence successful colonization is unlikely. In tropics and subtropics, habitat suitability of C. gestroi is high. We speculate that continuous urbanization and increasing human population will increase its introduction frequency and cause further extension in fast developing tropical and subtropical countries.

Managing social insects of urban importance.

Social insects have a tremendous economic and social impact on urban communities. The rapid urbanization of the world has dramatically increased the incidence of urban pests. Human commerce has resulted in the spread of urban invasive species worldwide such that various species are now common to many major urban centers. We aim to highlight those social behaviors that can be exploited to control these pests with the minimal use of pesticides. Their cryptic behavior often prohibits the direct treatment of colonies. However, foraging and recruitment are essential aspects of their social behavior and expose workers to traps, baits, and pesticide applications. The advent of new chemistries has revolutionized the pest management strategies used to control them. In recent years, there has been an increased environmental awareness, especially in the urban community. Advances in molecular and microbial agents promise additional tools in developing integrated pest management programs against social insects.

A comparison of tunnel geometry between the Formosan subterranean termite and the Asian subterranean termite (Blattodea: Rhinotermitidae).

BACKGROUND: Stake surveys and in-ground monitoring stations have been widely used to study field populations of many subterranean termite species, but thus far they have never been intercepted by the invasive Asian subterranean termite, Coptotermes gestroi (Wasmann), in southeastern Florida. To investigate the reasons for the inability of C. gestroi to intercept these in-ground monitoring devices, we compared its tunnel geometry with that of the Formosan subterranean termite, Coptotermes formosanus Shiraki. Two-year-old incipient colonies of both species confined in simulated structural infestations were connected to planar arenas containing four wooden discs. RESULTS: Coptotermes formosanus colonies constructed more abundant and more complex tunnel networks and intercepted more wooden discs than C. gestroi. C. formosanus propagated shorter primary tunnels and longer secondary tunnels with more branching frequency than C. gestroi, and probably adopted an area searching strategy to search for food in an area before moving on to other areas. In comparison, C. gestroi used a distance searching strategy by constructing linear and long primary tunnels to search for food at distance. CONCLUSIONS: Because tunnels of C. gestroi were less abundant and they tend to travel straight for some distance, they may have bypassed survey stakes or in-ground monitoring stations that are sparsely distributed in soil. The tunnel geometry of C. gestroi may explain why none of these in-ground monitoring devices has been intercepted by this species in southeastern Florida. © 2023 Society of Chemical Industry.

A comparison between above-ground bait stations and experimental caulk baits for elimination of field colonies of the Asian subterranean termite, Coptotermes gestroi (Blattodea: Rhinotermitidae).

Survey stakes and in-ground (IG) stations have failed to intercept underground tunnels of the Asian subterranean termite, Coptotermes gestroi (Wasmann), in southeastern Florida, rendering nearly useless the IG bait station that is the main tool of commercial baiting systems. When placed over an active infestation, above-ground (AG) bait stations were readily fed on by C. gestroi, resulting in colony elimination. A new experimental type of AG bait application being studied is an injectable caulk bait. In this study, we compared the efficacy of AG bait stations and an experimental AG caulk bait against field colonies of C. gestroi. Following the applications of AG bait stations at 3 sites with infested houses and trees, C. gestroi colonies were eliminated 7.1-28.1 wk later. The experimental AG caulk bait was applied at 7 sites including 4 houses, 2 office buildings, and 1 docked sailboat. Colony elimination times at caulk bait sites ranged from 3.1 to 13.6 wk, but there was no statistical difference in mean colony elimination time between AG station bait sites (17.4 ± 10.5 wk) and AG caulk bait sites (8.4 ± 3.8 wk). This study showed that AG caulk bait applications were equally efficacious in eliminating existing C. gestroi in structures as AG bait stations and will offer another tool for termite control professionals to better manage subterranean termites including C. gestroi.