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Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P, Grimaldi, David A (2023): COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA. Bulletin of the American Museum of Natural History 459 (1): 1-184, DOI: 10.5531/sd.sp.55, URL: http://dx.doi.org/10.5531/sd.sp.55

Intrinsic dinitrogen (N2) fixation by diazotrophic bacteria in termite hindguts has been considered an important pathway for nitrogen acquisition in termites. However, studies that supported this claim focused on measuring instant N2 fixation rates and failed to address their relationship with termite colony growth and reproduction over time. We here argue that not all wood-feeding termites rely on symbiotic diazotrophic bacteria for colony growth. The present study looks at dietary nitrogen acquisition in a subterranean termite (Rhinotermitidae, Coptotermes). Young termite colonies reared with wood and nitrogen-rich organic soil developed faster, compared to those reared on wood and inorganic sand. More critically, further colony development was arrested if access to organic soil was removed. In addition, no difference of relative nitrogenase expression rates was found when comparing the hindguts of termites reared between the two conditions. We therefore propose that subterranean termite (Rhinotermitidae) colony growth is no longer restricted to metabolically expensive intrinsic N2 fixation, as the relationship between diazotrophic bacteria and subterranean termites may primarily be trophic rather than symbiotic. Such reliance of Rhinotermitidae on soil microbial decomposition activity for optimal colony growth may also have had a critical mechanistic role in the initial emergence of Termitidae.

Several species of drywood termites, subterranean termites, and fungus-growing termites cause extensive economic losses annually worldwide. Because no universal method is available for controlling all termites, correct species identification is crucial for termite management. Despite deep neural network technologies’ promising performance in pest recognition, a method for automatic termite recognition remains lacking. To develop an automated deep learning classifier for termite image recognition suitable for mobile applications, we used smartphones to acquire 18,000 original images each of four termite pest species: Kalotermitidae: Cryptotermes domesticus (Haviland); Rhinotermitidae: Coptotermes formosanus Shiraki and Reticulitermes flaviceps (Oshima); and Termitidae: Odontotermes formosanus (Shiraki). Each original image included multiple individuals, and we applied five image segmentation techniques for capturing individual termites. We used 24,000 individual-termite images (4 species × 2 castes × 3 groups × 1,000 images) for model development and testing. We implemented a termite classification system by using a deep learning–based model, MobileNetV2. Our models achieved high accuracy scores of 0.947, 0.946, and 0.929 for identifying soldiers, workers, and both castes, respectively, which is not significantly different from human expert performance. We further applied image augmentation techniques, including geometrical transformations and intensity transformations, to individual-termite images. The results revealed that the same classification accuracy can be achieved by using 1,000 augmented images derived from only 200 individual-termite images, thus facilitating further model development on the basis of many fewer original images. Our image-based identification system can enable the selection of termite control tools for pest management professionals or homeowners.

In the eastern United States, there are nine species of subterranean termites in three genera: Reticulitermes (six species), Coptotermes (two species), and Prorhinotermes (one species). These species serve as important ecological players by decomposing cellulose material, and some are important structural pests. Many of these species are difficult to discriminate morphologically and require examining the reproductive or soldier castes, which can be difficult to collect. While some genetic tools have been developed for species identification, they are often expensive and time-consuming. To help facilitate identification, we developed a more cost-effective and rapid genetic method to identify Reticulitermes species by screening 10 PCR primers that amplified inter-simple sequence repeats (ISSRs) in other termite species. From these, one primer was amplified in all five focal Reticulitermes species and contained conserved, species-specific fragments. We further screened this identification method on samples of each species covering a diversity of mitochondrial DNA haplotypes and localities. This identification method utilizing ISSRs can be used to quickly identify five species of Reticulitermes subterranean termites in the eastern United States in a matter of hours, providing a useful technique for pest management as well as future ecological research.

Termites are intimately tied to the microbial world, as they utilize their gut microbiome for the conversion of plant cellulose into necessary nutrients. Subterranean termites must also protect themselves from the vast diversity of harmful microbes found in soil. However, not all soil microbes are harmful, such as Streptomyces and methanotrophic bacteria that some species of termites harbor in complex nest structures made of fecal material. The eastern subterranean termite, Reticulitermes flavipes, has a simple nest structure consisting of fecal lined galleries. We tested the hypothesis that R. flavipes maintains a select microbial community in its nests to limit the penetration of harmful soilborne pathogens and favor the growth of beneficial microbes. Using Illumina sequencing, we characterized the bacterial and fungal communities in the surrounding soil, in the nest galleries, and on the cuticle of workers. We found that the galleries provide a more beneficial microbial community than the surrounding soil. Bacterial and fungal diversity was highest in the soil, lower in the galleries, and least on the cuticle. Bacterial communities clustered together according to the substrate from which they were sampled, but this clustering was less clear in fungal communities. Most of the identified bacterial and fungal taxa were unique to one substrate, but the soil and gallery communities had very similar phylum-level taxonomic profiles. Notably, the galleries of R. flavipes also harbored both the potentially beneficial Streptomyces and the methanotrophic Methylacidiphilales, indicating that these microbial associations in fecal material pre-date the emergence of complex fecal nest structures. Surprisingly, several pathogenic groups were relatively abundant in the galleries and on the cuticle, suggesting that pathogens may accumulate within termite nests over time while putatively remaining at enzootic level during the lifetime of the colony.

Several termite species are significant economic pests, causing damage to wood in both man-made structures and also in forest ecosystem. The species belongs to genus Coptotermes (Rhinotermitidae: Isoptera: Blattodea) are widespread and few of them are among the world’s most dangerous wood pests. Two species of Coptotermes were collected, identified and described from yemene, mora and tali logs imported from Columbia, Suriname and Equitorial Guinea. These two intercepted species are non-native to India which are Coptotermes testaceus (Linnaeus) and Coptotermes sjostedti Holmgren. Identification was initially made with morphological characters and then with molecular DNA barcoding for a 348 bp fragment of 16S rRNA gene. Maximum likelihood Phylogenetic analysis results showed that data recovered as monophyletic which confirms the species identity. Coptotermes testaceus and C. sjostedti are in single clade. Coptotermes testaceus is neotropical in origin and C. sjostedti is native to Africa. Both the species are known to be serious pests in human habitats and forest ecosystem in the regions of their distributions. This first interception suggests possible chances of entry and establishment in India and provides an important alert for authorities concerned to take the necessary steps in monitoring and preventing its possible introduction. The importance of quarantine and potential infliction of damage they may cause if unnoticed and future measures to be taken are discussed.

Oceanic rafting through driftwood has been hypothesized to be a mechanism underlying the transoceanic distribution of termites (Order: Blattodea). To test this hypothesis, we examined the salinity tolerance of 12 termite species from eight genera and three families, namely Archotermopsidae, Kalotermitidae, and Rhinotermitidae. Our results revealed that the survival rates of Incisitermes inamurai (Oshima), Cryptotermes domesticus (Haviland), Prorhinotermes flavus (Bugnion and Popoff), P. simplex (Hagen), and Heterotermes sp. are not affected by treatment with 3.5% saline water, strongly supported that oceanic rafting may be a mechanism underlying the insects' transoceanic distribution. By contrast, Hodotermopsis sjostedti Holmgren, Glyptotermes satsumensis (Matsumura), Coptotermes formosanus Shiraki, Co. gestroi (Wasmann), Reticulitermes virginicus (Banks), R. leptomandibularis Hsia and Fan, and R. kanmonensis Takematsu treated with saline water showed dehydration symptoms, and their mortality rates increased significantly within 12 days after treatment. These results indicate that these species are less likely to be dispersed through oceanic driftwood and that their transoceanic dispersal is rather more likely to occur through human transportation or land bridges. Phylogenetic positions and habitats of salinity‐tolerant termites implied that the acquisition of salinity tolerance may relate to both phylogeny and coastal living.

Social insects produce complex nest structures as a result of the repetition of simple behaviors by many individuals. Individual actions are often consistent across different socio-environmental conditions, which enables colonies to build a variety of structures with minimal change in behavior. In this study, we show that the individual building behavior of termites can be a species-specific trait shared even between distinct morphological castes. Subterranean termites engage in soil excavation in two different contexts in their life history: foraging for resources by workers and initial nest excavation by colony foundation pairs. Our comparison of tunneling behaviors by colony founders of three different species revealed distinct transporting mechanisms; Heterotermes aureus (Snyder) (Isoptera: Rhinotermitidae) and Gnathamitermes perplexus (Banks) (Isoptera: Termitidae) carry sand particles using only their mandibles, while Paraneotermes simplicicornis (Banks) (Isoptera: Kalotermitidae) use their legs to kick sand particles backward. The observed behaviors are consistent with those of workers in each species, despite a substantial dimorphism of body size, especially in G. perplexus. Furthermore, the behavioral difference is associated with distinct tunnel development and task allocation patterns among species. Our study suggests that the nest building behavior of termites varies little with context or function within a species but can change among species, emphasizing the fruitfulness of comparative studies in future research.

African termites are classified into five distinct families, Termitidae, Rhinotermitidae, Hodotermitidae, Termopsidae and Kalotermitidae. Termites are undoubtedly one of the key ecosystem engineers...

Subterranean termites are an ancient group of social insects, broadly spread, known primarily as economically important pests for the destruction of wooden structures and also as agricultural pests. Many of the banned chlorinated hydrocarbon insecticides used to be recommended for the control of termites. Hence, it has become necessary to find alternative measures for termite control in the natural diverse habitats as well as in the cultivated soil to diminish use of these chemicals. Therefore, in the present study, 4 strains of entomopathogenic nematodes (EPN) belong to the genus Steinernema were assessed against Coptotermes heimi (Wasmann). These EPN included Steinernema pakistanense NNRC-AS.04, S. siamkayai NNRC-As.12, S. bifurcatum NNRC-As.65, and S. maqbooli NNRC-As.88. Virulence of all strains was determined at 3 different EPN inocula in plastic containers layered with sand. A significant nematode inoculum effect was detected for all the tested EPN species. NNRC-AS.04 and NNRC-As.65 showed the highest virulence effects of 95 and 100%, respectively at 150 IJs/ml.

Termite colony size can influence its foraging activity, reproductive maturity, and, for pest species, potential for structural damage. Estimating colony size of subterranean termite species in field conditions has been challenging owing to their extensive foraging territory and their cryptic nesting habit and has primarily relied on mark–recapture methods. With laboratory-reared colonies in individual containers, determining colony size can be achieved by processing all termites from the nest material, which can be labor intensive and partially destructive. However, with the recent rise in the need of large laboratory colonies for use in colony-wide experimental protocols, there was an imperative to develop a procedure to estimate initial colony sizes without imposing a major stress on colonies before an experiment. In this study, the average daily wood consumption of whole colonies was used to infer the colony size of two Coptotermes, Wasmann (Blattodea: Rhinotermitidae) species and their hybrids in laboratory-rearing conditions. Correlations between the daily wood consumption and several demographic variables within colonies were established. Linear models varied across all species mating types with R2 values greater than 0.8 for all demographic variables. For colonies from all mating combinations, Pearson’s correlation coefficient values were greater than 0.94 between their daily wood consumption and both the number of workers and total number of termites, and greater than 0.91 between daily wood consumption and colony mass. Therefore, in colonies with fixed laboratory conditions, their average daily wood consumption determination, which is nondestructive on colonies, can be used to infer colony size of subterranean termites.

Concerns on efficacies of termiticides used for soil treatment to prevent Formosan subterranean termite (Coptotermes formosanus Shiraki) infestations have prompted pest control companies to suggest that retreatments are necessary after flooding of homes. Therefore, to address concerns about the efficacy of termiticides after flooding, we designed a flooding simulation experiment in the laboratory. We used four formulated termiticides containing fipronil, imidacloprid, chlorantraniliprole, or bifenthrin as active ingredients (a.i.) and two colonies of field-collected C. formosanus for this study. Evaluations of each chemical at concentrations of 1, 10, and 25 ppm in both sand and soil were conducted in the laboratory by comparing termite mortalities in no-choice bioassays after exposure to flooded (for 1 wk) and unflooded substrates. Toxicity from bifenthrin and fipronil were not affected by flooding regardless of substrate type except at the lowest concentration tested. Toxicity from chlorantraniliprole was lower in flooded sand at 1 ppm but otherwise similar among flooding treatments. In flooded soil, toxicity from chlorantraniliprole was low at 1 ppm, but unexpectedly high in flooded conditions at 10 and 25 ppm. For all concentrations of imidacloprid-treated sand, mortality of C. formosanus was reduced after a flood. However, like chlorantraniliprole, 10 and 25 ppm of imidacloprid-treated soil in flooded conditions resulted in an increased toxicity on C. formosanus. Our study supports the idea that chemicals with a higher water solubility like imidacloprid may require a home to be retreated with less water-soluble termiticides or baits after a flood.

Metagenomics and transcriptomics have had some success analyzing community and functional ecology of the termite gut, but carbon utilization ecology and the effect of diet on the gut community are not well understood. This study was done to determine the effect of three hardwood tree types, oak (Quercus spp.), red maple (Acer rubrum), and tupelo (Nyssa aquatica) on the termite species, Reticulitermes flavipes in the family Rhinotermitidae. Termite abdomen homogenates were incubated on agar plates containing three common carbon sources in the termite gut, namely, acetate, cellobiose, and phenol under aerobic and anaerobic conditions. Bacterial growth was higher on cellobiose than any other carbon source. Higher bacterial growth on cellobiose was observed from termite colonies feeding on oak than on phenol from the other two wood types. The difference between aerobic and anaerobic conditions was not significant. A bacterium, Acinetobacter tandoii isolated and identified from our previous study was subjected to high concentrations of phenol as the sole carbon source and this bacterium was able to degrade phenol concentration up to 600 mg/L.

As a social insect, termites have different castes and division of labor in a colony. Investigating the social behavior of subterranean termites is a challenge due to the cryptic nature and large colony size. Planar arenas are commonly used to study these termites under laboratory conditions, and have provided several advantages. However, there is no means to designate areas such as a royal chamber or central nest from foraging sites because reproductives can move freely across arenas. In this study, we examined the minimum passing size of different castes of Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), in order to develop a reproductive excluder and correlated minimum passing size with head widths and heights. We found that workers and soldiers of C. formosanus were able to pass through a gap greater than or equal to 0.7 mm. Our results showed that there are significant differences in the head width and height based on castes and head height was more critical than head width to determine passing size. We further confirmed feasibilities of the reproductive excluders using incipient colonies of C. formosanus. Confining reproductives using the excluder in laboratory experiments will provide more chances to study the royal chamber and central nest independently of foraging sites.

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.

Laboratory studies of Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae) often employ the use of field-collected foraging populations of individuals as defined colonies. The biological relevance of this practice is often called into question, because these colonies lack a full composition of reproductive castes and brood, which may have physiological and behavioral consequences. Rearing intact laboratory colonies can be done; however, it is time-consuming and labor-intensive. The artificial fusion of field-collected foraging populations with a young, laboratory-reared incipient colony may provide whole, intact colonies for laboratory research. The current study measures survivorship of fused colonies using laboratory-reared complete incipient colonies ranging in age from 0 to 5 mo, fused with 100 workers and 10 soldiers from field-collected populations of different colonial origin. Results indicate that 60% of colony fusion was successful when the incipient colony introduced is 5 mo of age. This method of colony fusion will provide researchers with intact colonies using minimal resources.

There are 28 invasive termite species, most belong to two families, the Kalotermitidae (esp. Cryptotermes spp.) and Rhinotermitidae (esp. Coptotermes spp.). Six invasive termite species are known to have spread into natural habitats, but little direct research has been conducted into their ecological impacts. Predictions based on indirect research (natural durability of commercial wood species) suggest fast-growing, pioneer tree species with low density wood, perhaps notably legumes, are most vulnerable to invasive termites, but even slow growing climax tree species may succumb. Cryptotermes will likely have less ecological impact, due to small colonies attacking dead branch stubs in the canopy. Coptotermes will likely have greater impact, due to large colony sizes and nesting in living trees, which they hollow out and can kill. There are no studies of invasive termites on native termites, other wood-eating insects, or predators, such as ants, showing considerable scope for future research.

A new infestation of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), was discovered in Canyon Lake, Riverside County, California. We used three mitochondrial DNA (COI, COII, and 16S) and seven polymorphic microsatellite markers to characterize the genetic relationship of the colony with two other colonies that were collected in 1992 and 2018 in La Mesa, San Diego County. Maximum likelihood phylogeny of C. formosanus based on concatenated COI and COII sequences revealed that the two La Mesa populations (CA01 and CA02) and the Canyon Lake population (CA03) were from different maternal lineages. Based on the 14 COII haplotypes of C. formosanus found world-wide, CA01 and CA02 belonged to a haplotype widely distributed across the United States, while CA03 was grouped under a haplotype predominantly found in Asia. Microsatellite allele frequencies across all loci for both La Mesa populations were relatively similar, but significant genetic differences were found between CA02 and CA03 colonies (FST = 0.24; Dest = 0.30; G″ ST = 0.55; P < 0.01).

The development of baits for subterranean termite control over the past 25 yr has provided cost-effective alternatives to liquid termiticide treatments. Current bait products use one of the few available benzoylurea chitin synthesis inhibitors (CSIs) labeled for subterranean termites. These insecticides are used because of their nonrepellency, their slow-acting mode of action, and their dose-independent lethal time. Although many studies have provided ample evidence of the efficacy of CSI baits for subterranean termite colony elimination, most have focused on hexaflumuron and noviflumuron. However, bait products using alternative CSIs have not received the same level of scrutiny, limiting the amount of evidence proving their efficacy. One such compound is novaluron, the active ingredient currently used in the Trelona ATBS—Advance Termite Baiting System bait product. The current study independently tested the efficacy of this commercially available bait formulation against whole colonies of Coptotermes gestroi (Wamann) (~63,910 workers) in the laboratory, using an extended experimental setup to simulate a 15-m foraging distance from the central part of the nest to the bait, while having access to alternative food sources. Treated colonies progressively ceased to feed on wood items within 45 d after being provided access to the novaluron bait formulation, with a subsequent progressive collapse of the population, leading to colony elimination by 91 d. This study therefore confirms the efficacy of novaluron baits against subterranean termites, and currently remains one of the few CSIs that can be applied for the successful control of Coptotermes infestations.

Climate change impacts the current and potential distribution of many insects, since temperature is often a limiting factor to where the insects can survive. The Formosan subterranean termite, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), has never been reported in South Korea despite its close proximity to 2 countries (China and Japan) where this economically important pest has been reported. This may be due to the average winter temperature in South Korea which is below 4 °C, the lower limit of the current distribution range of Formosan subterranean termite. However, with climate change leading to increased temperatures, South Korea may be susceptible to successful invasion by Formosan subterranean termite. The objective of this study is to estimate the future possible distribution of Formosan subterranean termite in Korea based on temperature. Climate data from Korea showed a significant increase of 2.19 °C per 100 yr in average annual temperature from 1910 to 2018. Previous and current average winter temperatures were higher than 4 °C only in Jeju, and most provinces did not exceed 4 °C, except for some southern cities such as Busan in 2000 to 2019. With the estimated rate of temperature rises, winter temperatures in Gyeongsangnam-do will exceed 4 °C starting from 2020, and Jeollanam-do will exceed 4 °C from 2060. Coupled with the statistically significant, increased annual trade between Korea and other countries (China, Japan, Taiwan, and the USA) where C. formosanus is currently distributed, we predict that Formosan subterranean termite will become established in South Korea, probably starting from a southern trade port such as Busan.

Termites, being vulnerable to parasitic or pathogenic infections due to large number of individuals living together in colonies, have evolved various behavioral and physiological tactics to resist the infections by those pathogens. Locomotion can help termites collect information on parasites and accordingly exhibit hygienic behaviors. Termites inevitably encounter entomopathogenic fungi during nesting and foraging. However, how these fungal pathogens influence locomotion of termites and how hygienic behavior benefits their survival remains unknown. Here, we examined locomotion alteration of the termite Reticulitermes chinensis (Isoptera: Rhinotermitidae) after infections with different concentrations of the entomopathogenic fungus Metarhizium anisopliae (Hypocreales: Clavicipitaceae). When R. chinensis was isolated, the low concentration (5 × 103 conidia/ml) significantly increased termite locomotion after 6, 12, and 24 h compared with control. However, the high concentrations (5 × 107, 5 × 109 conidia/ml) significantly decreased termite locomotion after 48 h, and termite survival was also significantly lower at 5 × 107 and 5 × 109 conidia/ml compared with the low concentrations and the control. When R. chinensis was in group, however, the locomotion significantly increased 24 h after exposure to 5 × 103 and 5 × 109 conidia/ml but was normalized after 48 h of exposure compared with the control. Allogrooming was significantly higher at 5 × 103 and 5 × 109 conidia/ml compared with the control. The fungal infection did not result in significantly higher mortality of the group termites probably owing to their allogrooming. These findings enhance our understanding on how a termite species copes with biotic stress (i.e., fungal infections) via adaptive behaviors.

The Formosan subterranean termite, Coptotermes formosanus Shiraki, 1909, is a highly destructive structural pest endemic to East Asia. We report a land-based establishment of C. formosanus in Petah Tikva, Israel, over 6000 km from its nearest previous locality in China. The species’ identity was confirmed by soldier morphology and by COI sequence data. In addition, a population discovered in 1992 in suburban San Diego, California, USA, remains viable. Marathon hosts the first infestation of C. formosanus in the Florida Keys. The world distribution of C. formosanus is presented, and the biogeography and mechanisms of spread of this termite are discussed.

Coptotermes testaceus (L.) (Rhinotermitidae) is a subterranean termite species that causes damage in urban and agricultural areas in the neotropics. Despite its economic importance, there are no studies on its basic biological aspects for laboratory management and the development of strategies for its control. The objective of the present study was to evaluate the relative humidity, temperature, substrate moisture and preference to different wood substrates for the best C. testaceus survival under laboratory conditions. For this, a range of eight relative humidity (from 9 to 100%), three temperatures (20, 25 and 30 °C), six substrates (Pinus sp, Cedrela odorata (L.), Cocos nucifera (L.), Eucalyptus urophylla (S. T. Blake), Haematoxylum campechianum (L.) and Tabebuia rosea [Bertol.] DC) and four substrate moistures, (0 to 60%) were tested. The results of this study indicated a significant effect of all factors on termite survival or termite preference. When tested independently, the highest survival percentage of C.testaceus was obtained with humidity of 100%, temperature of 20 °C, substrate moisture of 60% and the Eucalyptus urophylla substrate, reaching 83.33% survival at 21 days of observation. With these preliminary assays on small termite groups, it is concluded that with the appropriate percentages of humidity, temperature and substrate and the interaction of these three factors, further research can be conducted using larger termite groups in biologically relevant conditions, in order to study various aspects of C. testaceus biology.

Reduced genetic diversity through inbreeding can negatively affect pathogen resistance. This relationship becomes more complicated in social species, such as social insects, since the chance of disease transmission increases with the frequency of interactions among individuals. However, social insects may benefit from social immunity, whereby individual physiological defenses may be bolstered by collective‐level immune responses, such as grooming or sharing of antimicrobial substance through trophallaxis. We set out to determine whether differences in genetic diversity between colonies of the subterranean termite, Reticulitermes flavipes, accounts for colony survival against pathogens. We sampled colonies throughout the United States (Texas, North Carolina, Maryland, and Massachusetts) and determined the level of inbreeding of each colony. To assess whether genetically diverse colonies were better able to survive exposure to diverse pathogens, we challenged groups of termite workers with two strains of a pathogenic fungus, one local strain present in the soil surrounding sampled colonies and another naïve strain, collected outside the range of this species. We found natural variation in the level of inbreeding between colonies, but this variation did not explain differences in susceptibility to either pathogen. Although the naïve strain was found to be more hazardous than the local strain, colony resistance was correlated between two strains, meaning that colonies had either relatively high or low susceptibility to both strains regardless of their inbreeding coefficient. Overall, our findings may reflect differential virulence between the strains, immune priming of the colonies via prior exposure to the local strain, or a coevolved resistance toward this strain. They also suggest that colony survival may rely more upon additional factors, such as different behavioral response thresholds or the influence of a specific genetic background, rather than the overall genetic diversity of the colony., Reduced genetic diversity through inbreeding can negatively affect pathogen resistance. We investigated this hypothesis in termites by testing whether the level of inbreeding within a colony affected the survival of workers challenged with two fungal pathogens. We found a bimodal distribution of colony survival, whereby colonies exhibit either high or low susceptibility. However, this difference was not explained by the level of inbreeding within the colony, suggesting that colony immunity may rely more on a specific genetic background, rather than its overall genetic diversity.

Sophisticated social behaviors in termite colonies are mainly regulated via chemical communication of a wide range of pheromones. Trail pheromones play important roles in foraging behavior and building tunnels and nests in termites. However, it is almost unclear how termites perceive trail pheromones. Here, we cloned and sequenced of olfactory co-receptor (Orco) genes from the two termites Reticulitermes chinensis Snyder (Isoptera: Rhinotermitidae) and Odontotermes formosanus (Shiraki) (Isoptera: Termitidae), and then examined their responses to trail pheromones after silencing Orco through RNA interference (RNAi). We found that Orco knockdown impaired their ability to perceive trail pheromones and resulted in the disability of following pheromone trails in the two termite species. Our locomotion behavior assays further showed that Orco knockdown significantly decreased the distance and velocity in the two termite species, but significantly increased the angular velocity and turn angle in the termite R. chinensis. These findings strongly demonstrated that Orco is essential for termites to perceive their trail pheromones, which provides a potential way to control termite pests by damaging olfactory system.

Moisture conditions of food and soil are essential for the survival and foraging activities of subterranean termites. Polyacrylamide/attapulgite composite is a water-retaining agent that has been applied to increase moisture of agricultural soils. We hypothesize that polyacrylamide/attapulgite composite may increase the moisture of bait matrixes and soil surrounding baiting containers and therefore attract termites and increase their foraging activities. In the present study, aggregation and feeding preferences, survivorship, body water percentage, and wood consumption of Formosan subterranean termites, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), were investigated when responding to polyacrylamide/attapulgite composite that was buried within soil (substrate) or filled in the void volume of baiting containers. Two-choice tests showed that termites consumed significantly more wood when polyacrylamide/attapulgite composite was buried within dry soil (27%-moisture) than the controls (no polyacrylamide/attapulgite composite was provided). However, polyacrylamide/attapulgite composite buried within wet soil (54%-moisture) did not significantly affect foraging behaviors of termites. Multiple-choice tests showed no aggregation or feeding preference of termites in the baiting containers filled with polyacrylamide/attapulgite composite compared with the soil-filled or unfilled ones, whenever the substrate was dry or wet. No-choice tests showed that the presence of polyacrylamide/attapulgite composite (buried within soil or filled in baiting containers) significantly increased wood consumption and body water percentage of termites as well as wood moisture under dry-substrate conditions. Our studies suggest that burying polyacrylamide/attapulgite composite within dry soil may enhance foraging activities of termites, but filling the bait stations with polyacrylamide/attapulgite composite may not effectively attract termites.

This study evaluated the impact of a non-repellent liquid termiticide (fipronil) and a chitin synthesis inhibitor (CSI) termite bait (noviflumuron) on whole colonies of Coptotermes gestroi (Wasmann) (Blattodea: Isoptera: Rhinotermitidae) in laboratory conditions, over a 12-m foraging distance. The protocol simulated the implementation of remedial treatment of an infested structure, where the colony has multiple access routes, and where only a portion of the population was directly exposed to the treatment. Within 2 wk after the implementation of fipronil, all termites within 1.5 m away from the treatment died. The accumulation of cadavers near the treated area resulted in secondary repellency and the colonies avoided the treated area for the remaining 10 wk of the experiment, using alternative foraging galleries. At the end of the 12 wk, colonies exposed to fipronil did not have any difference in population size compared with control colonies. Comparatively, colonies exposed to noviflumuron had no change in foraging activity for the first ≈40 d, but then termites progressively ceased their activity throughout their foraging territory. By 12 wk, noviflumuron-exposed colonies were near-elimination, with only a few workers, soldiers remaining, and all colonies were eliminated by 95 d. This study shows that subterranean termite colonies with access to CSI baits are inevitably eliminated, regardless of the position of the bait, while colonies exposed to fipronil are only locally excluded from the area near the treatment, but may maintain their foraging activity in untreated areas, and retain their potential risk for structural damage in the long term.

Subterranean termites often transport soil into bait stations. In this study, we hypothesize that adding soil or clay material in the bait may affect preference and performance of termites. Choice and no-choice tests were conducted in the laboratory to investigate the aggregation and feeding preference, survivorship, wood consumption, and body water percentage of termites in response to food containers (here we simulated the bait station by placing a wood block into a bigger plastic box with termite-entering holes on the wall) with the void space filled with soil (sandy clay loam), clay material (sodium bentonite), or remained unfilled. Choice tests showed that under low-moisture conditions, food containers filled with clay attracted significantly more termites (Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae) and Reticulitermes guangzhouensis Ping (Blattodea: Rhinotermitidae)) compared to food containers filled with soil, or unfilled. Under medium-moisture conditions, however, the percentages of termites that aggregated in the food containers filled with soil or clay were similar, and both were significant higher than the percentages in unfilled ones. In no-choice tests, the highest survivorship and wood consumption in C. formosanus were recorded under medium-moisture conditions and when food containers were filled with clay, whereas the lowest survivorship and wood consumption were recorded under low-moisture conditions and when food containers were filled with soil. Interestingly, presence of clay increased the body water percentage of termites. Our study enhances the understanding of the foraging ecology of subterranean termites, and may contribute to the improvement of termite-baiting technologies.

Heartwood extract from white mulberry (Morus alba L.) (Rosales: Moraceae) were investigated for antitermitic activity against Reticulitermes flavipes (Kollar) (Blattodea: Rhinotermitidae) in laboratory experiments. An ethanol:toluene (2:1) solvent system was used to remove extract from heartwood shavings. A concentration-dependent feeding response and mortality were observed for termites exposed to a concentration series range of 1.25 to 10 mg/ml of extract based on their dry weight. Results showed that maximum termite mortality occurred at 10 mg/ml. Based on the concentration series data, LC50 was calculated at 1.71 mg/ml. In filter paper feeding and repellency assays, extract significantly decreased the total number of gut protozoa compared with untreated and solvent controls. After feeding on filter paper treated at 10 mg/ml for 2 wk, protozoan populations were reduced by >55%. In choice and no-choice tests with mulberry heartwood, greater wood loss from termite feeding was found on solvent extracted blocks compared with nonextracted. Complete (100%) mortality was observed after feeding on nonextracted blocks compared with extracted blocks. Heartwood extract from white mulberry imparted resistance to vacuum pressure treated, nondurable southern pine and cottonwood. At every concentration tested, 100% mortality was observed after feeding on extract-treated southern pine or cottonwood. GC-MS analysis of extract showed high levels of the phenol compound, resorcinol. Results indicated that heartwood extract from white mulberry have antitermitic properties and might be potentially valuable in the development of environmentally benign termiticides.

Laboulbeniopsis termitarius (Thaxt) and Antennopsis gallica (Buchli and Heim) are two of the most common ectoparasitic fungi found on the body surface of termites. While visual observation under a dissecting microscope is a common method used to screen for such fungi, it generally requires a large number of termites and is thus very time consuming. In this study, we develop a fast, efficient protocol to detect fungal infection on the termite Reticulitermes speratus (Kolbe). Species-specific primers were designed based on sequence data and amplified using a number of universal fungus primer pairs that target partial sequences of the 18s rRNA gene of the two fungi. To detect these fungi in a robust yet economic manner, we then developed a multiplex nested polymerase chain reaction assay using species-specific primers. Results suggested that both fungi could be successfully detected, even in cases where L. termitarius was at low titer (e.g., a single thallus per termite). The new method described here is recommended for future surveys of these two fungi, as it is more sensitive, species specific, and faster than visual observation, and is likely to facilitate a better understanding of these fungi and their dynamics in host populations.

Heterotermes indicola (Wasmann) (Blattodea: Rhinotermitidae) is a species of subterranean termite that is a destructive pest of wood and wood products in Pakistan. This study evaluated the antioxidant and antienzyme potential of heartwood extractives against H. indicola. Heartwood extractives of four durable wood species, Tectona grandis (L.f), Dalbergia sissoo (Roxb.), Cedrus deodara (Roxb.), and Pinus roxburghii (Sarg.) were removed from wood shavings via soxhlet extraction with an ethanol:toluene solvent system. The antioxidant potential of the extractive compounds was determined using the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging test. Results showed maximum antioxidant activity for extractives of D. sissoo. D. sissoo had the lowest IC50 (the concentration where 50% inhibition of the DPPH radical is obtained) at 28.83 µg/ml among the heartwood extractives evaluated. This antioxidant activity, however, was not concentration dependent as was observed in the other heartwood extractives tested. At the maximum test concentration, T. grandis showed the highest percent inhibition at 89.7%, but this inhibition was lower compared to the positive control antioxidant compounds butylated hydroxytoluene and quercetin. When termites were fed filter paper treated with IC50s of the extractives and control compounds, glutathione S-transferase activity in the guts of H. indicola workers was significantly reduced by T. grandis and D. sissoo extractives. Similarly, esterase activity was reduced more by P. roxburghii extractives compared to control antioxidant treatments and other tested extractives. However, none of the extractives examined significantly reduced the activity of catalase enzymes in H. indicola compared to treatments with the antioxidant control compounds.

Western Ghats of Karnataka, an important biodiversity hot spot in the world, rich in insect fauna including termites. Diversity of termites from this region poorly understood. In the present study, we have redescribed 12 species and termites belonging to two families viz., Rhinotermitidae and termitidae based on morphological and molecular differences employing mitochondrial 16s rRNA. Further we have employed Bayesian inference in order to understand phylogenetic relationships among different termite species studied. The integrative taxonomic approach was successful in delimiting the species studied in the present investigation.

In addition to being a structural pest, the Asian subterranean termite, Coptotermes gestroi (Wasmann) (Blattodea [Isoptera]: Rhinotermitidae), appears to be a serious pest of the native urban tree canopy of southeastern Florida. Asian subterranean termite colonies have the ability to cause feeding damage to a wide range of trees comprising the urban canopy, some potentially to a lethal level. Slash pine, Pinus elliottii Engelm. (Pinaceae), appears to be particularly susceptible to C. gestroi feeding damage, as the termites feed primarily on the outer layers of the wood, immediately beneath the bark, wounding live tissues and ultimately girdling the tree. In comparison, hardwood trees such as live oak, Quercus virginiana Mill. (Fagaceae), sustain damage to the heartwood at the center of the tree, resulting in a central cavity, but leaving the live tissue intact. Our results suggest that C. gestroi has the potential to kill pine trees within the local urban canopy, which may irreversibly alter the urban forest composition. In addition, many large trees in our survey have been consumed partially by mature C. gestroi colonies, potentially compromising their structural integrity. Some large oak trees that were extensively hollowed out by C. gestroi collapsed in 2017 during hurricane Irma. We discuss different potential approaches for protecting susceptible trees, as a comprehensive IPM strategy is needed for this invasive termite pest species, especially in the complex and extensive urban forest of southeastern Florida.

Cellulose digestion is an essential process of termites, and it is accomplished by three types of cellulases. β-Glucosidase (BG), one of the critical cellulases responsible for cellulose degradation and glucose production, has been considered as a potential target for pest management strategies. Previous experiments identified two new endogenous BG homologs, CfBG-Ia and CfBG-Ib, in the digestive system of Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). The objectives of this study were to assess the impact of RNA interference on CfBG-Ia and CfBG-Ib expression and on termite survival. We tested the expression profiles of worker termites which were injected with gene-specific double-stranded RNA (dsRNA, targeting one gene at a time) and a dsRNA cocktail (targeting CfBG-Ia and CfBG-Ib simultaneously). The expression of CfBG-Ib showed a sharp decline in both dsCfBG-Ib and dsRNA cocktail treatments. The expression of CfBG-Ia reduced quickly and significantly in the dsRNA cocktail treatment; while in dsCfBG-Ia treatment, it decreased on the fifth day. Results showed that treatment with the dsRNA cocktail caused greater inhibition of the transcript expression and a shorter response time. However, the expression of nontarget BG homologs was increased as the target BG homologs were being repressed during the testing period in dsRNA cocktail treatment. These results demonstrate that targeting cellulase-coding genes may be a potential strategy to inhibit termite digestion process, or at least dsRNA cocktails serve as a means for identifying the most susceptible target gene families or biological processes.

Termites play important roles in the ecosystem as detritivores and soil engineers. However,alterations of the forest could change the diversity and abundance of termites. The Agropark atUniversiti Malaysia Kelantan (UMK), Jeli Campus is an agricultural park that is surrounded bysecondary forest and rubber plantations. This study was conducted to determine the diversity andpest species composition of termites at Agropark, UMK. Standardized line transects 100m long ×2m wide and divided into 20 sections (5m long × 2m wide) were conducted at three differentsampling sites in May to September 2015. A total of 29 termite species from 13 genera weresuccessfully identified with relative abundance of 128 (total hits). Diversity indices show highdiversity and evenness among the termite species in the study area. The termites comprise offamily Termitidae (75.9%) and family Rhinotermitidae (24.1%). Subfamily Macrotermitinaerecorded higher a number of species (12 species, 78 hits) compared to other subfamilies recordedin this study. Wood feeders and epigeal mound builders dominated the termite assemblages. Thetotal pest termite species collected is 41.4% (12 species) while 58.6% (17 species) of termitespecies were non-pest species that provide good ecological services to Agropark, UMKKJ. Thepests are mainly from genera Coptotermes, Schedorhinotermes, Macrotermes, Microtermes andGlobitermes. The higher number of pest species shows the possibility of pest attacks to thebuildings around the Agropark. Precautions against termite attack should be taken earlier toprevent serious damage to buildings in the future.

The subterranean termiteReticulitermes grasseiClément causes lesions in the trunk ofQuercus suberL. by constructing feeding galleries, but no information is available regarding otherQuercusspecies from the Mediterranean region. This work aimed to study the suitability of the other main oak species of Mediterranean forests as a food resource forR. grassei. Two experiments, choice and non-choice feeding, were conducted lasting for 15, 30, and 45 days each. In the non-choice experiment, termites were offered one of the following food types:Quercus suber,Quercus ilexL.,Quercus fagineaLam, cork orPinus pineaL., which was considered the control. The choice feeding experiment used all the same food types listed above, supplied simultaneously in the same container. Food selection was examined by analysing the relationships over time between surviving termites and food consumption. The results indicated thatR. grasseicould be considered a generalist species, as it consumed the cork and wood of all oak species, as well as displaying a clear preference for soft wood (pine). Correlation analysis indicated that consumption was not dependent on wood density. Survival ofR. grasseiwas influenced by the time of exposure to different oak species, but a high survival rate was maintained over time in the pine treatment (upper 70% in the three experiments). Given these results, it can be concluded that all the oak species are a suitable food source forR. grassei.

BACKGROUND The lethal time of a chitin synthesis inhibitor (CSI) baited colony of Coptotermes formosanus Shiraki largely depends on the time for workers to molt after consuming a lethal dose. Given that termite molting biology can regulate the time for elimination of a baited termite colony, the objective of this study was to determine how the fasting period (an important element of worker's molting cycle) and the acquisition of lethal dose can impact the total elimination period for a colony. RESULTS Within 9 wk, noviflumuron eliminated the foraging population in the 30 m long foraging arena. However, mortality in treatment groups did not begin until the 11th day. The 10 d lag post treatment is the fasting period for workers to prepare for ecdysis on the 11th d during which mortality occurs under the effect of CSI. CONCLUSION This study shows that with the exception of successful molting events during the first 10 d after baiting, mortality amongst workers with lethal doses of noviflumuron in the next molt is inevitable. The 10 d fasting period can make up at least 22% of a molt cycle (=45 d for a fourth worker instar or lower) which can be a window of opportunity for a worker to escape from the effect of CSI baits, thereby, extending the total time for the colony elimination.

Termites (Isoptera) are widely believed to be one of the most desiccation-prone insects. They must combat desiccation by locating and efficiently conserving water resources. Termites have evolved morphological, physiological, and behavioral characteristics that aid in the tolerance of desiccation. In 3 studies using 4 termite species, water loss tolerance and relative humidity (RH) preferences of termites exposed to 5 different RH, as well as the use of different water sources, were examined. Our results showed that Coptotermes formosanus Shiraki (Rhinotermitidae) preferred and survived better at high RH and with readily available water sources. Neotermes jouteli (Banks in Banks and Snyder) (Kalotermitidae) also preferred a high RH, but was more capable of tolerating lower RH and a lack of free water than C. formosanus. Cryptotermes brevis Walker (Kalotermitidae) and Cryptotermes cavifrons Banks (Kalotermitidae) did not exhibit greater survival in a certain RH nor when exposed to various sources ...

Effects of ecdysone, 20-hydroxyecdysone (20E), and an ecdysone agonist, halofenozide, were tested against the Formosan subterranean termite, Coptotermes formosanus Shiraki, and the eastern subterranean termite, Reticulitermes flavipes (Kollar), in a 12-d no choice assay. Approximately 22-26% of R. flavipes and C. formosanus exhibited symptoms of hyperecdysonism, that is, "jackknife" position, when exposed to ecdysone and 20E at 1,000 ppm, respectively. High mortalities were recorded for both termite species in ecdysone and 20E at 100 and 1,000 ppm, but only at 10,000 ppm for halofenizide. Termites are known to move back to the central nest before the onset of ecdysis, and those that ingested lethal doses of chitin synthesis inhibitors (CSIs) die near the royal pairs, which partially accounts for the success of CSI baits to eliminate subterranean termite colonies. Because ecdysteroids and their agonists induce molting in termites, incorporation of these compounds into baits could potentially achieve the same colony elimination. This study showed that lethal time (12 d) of ecdysteroids and ecdysone agonist is shorter than that of a CSI (45 d); hence, the baiting time should be reduced by more than a month when they are incorporated in termite baits.

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.

A colony of Reticulitermes lucifugus from Apulia (SE Italian Peninsula) was recently observed to have partially consumed some polystyrene panels applied on a wall, and used like seat for termite nest. Further observations could allow to better understand if this colony is just able to physically consume and chew this plastic material, releasing it chemically intact after the passage throughout the termites’ digestive system, or if their microbiome could allow the insects to at least partially metabolize and degrade the ingested polystyrene fragments, as recently observed in a few other insects.