Polymorphic microsatellite loci in the European subterranean termite,Reticulitermes santonensis Feytaud

We report on the identification and characterization of two dinucleotide, two trinucleotide and eight tetranucleotide microsatellite DNA loci isolated from the European subterranean termite Reticulitermes santonensis. We tested the loci on 51–92 individuals from 46 colonies from different regions of France. Eleven loci were polymorphic with 2–8 alleles per locus and low observed heterozygosities (0.10–0.48). We also tested the loci on 17–20 individuals from 10 colonies in the closely related North American species R. flavipes and found significantly more alleles (2–9 alleles per locus) and higher observed heterozygosities (0.15–0.80) than in R. santonensis. The lower observed heterozygosities in R. santonensis are consistent with higher levels of inbreeding in these colonies due to the presence of numerous inbred replacement reproductives.     

DNA-based identification of the eastern subterranean termite, Reticulitermes flavipes (Isoptera: Rhinotermitidae)

A DNA-based system for the identification of Reticulitermes flavipes (Koller) was established based on the following criteria: adequate molecular variation, comprehensive specimen sampling, explicit morphological species identification, and cladistic analysis. Termite soldiers were identified by labral shape, and these specimens and associated pseudergates were used in subsequent molecular analyses. Mitochondrial DNA from the AT-rich region was sequenced for 173 R. flavipes, Reticulitermes hageni Banks and Reticulitermes virginicus (Banks) soldiers and pseudergates collected from several widely dispersed Texan localities. Cladistic analysis was performed after exploration of an optimal sequence alignment inclusive of DNA sequences from Texas and published sequences from Georgia and Canada. Among the Texan individuals, 29, 5, and 1 mitochondrial DNA haplotypes were identified respectively with R. flavipes, R. hageni, and R. virginicus. One haplotype from El Paso likely represented a different Reticulitermes species. Species were monophyletic; however, individual relationships were unresolved in a strict consensus of 700 most parsimonious trees. Texas haplotypes were isolated by distance, and a correlation between genetic and geographic distance was observed among the Texas, Georgia, and Canada haplotypes. These results suggest that the methods outlined in this study will allow for the identification of R. flavipes from localities between Texas and Canada.     

Trail Communication During Foraging and Recruitment in the Subterranean Termite Reticulitermes santonensis De Feytaud (Isoptera, Rhinotermitidae)

The search for food in the French subterranean termite Reticulitermes santonensis De Feytaud is organized in part by chemical trails laid with the secretion of their abdominal sternal gland. Trail-laying and -following behavior of R. santonensis was investigated in bioassays. During foraging for food termites walk slowly (on average, 2.3 mm/s) and lay a dotted trail by dabbing the abdomen at intervals on the ground. When food is discovered they return at a quick pace (on average, 8.9 mm/s) to the nest, laying a trail for recruiting nestmates to the food source. While laying this recruitment trail the workers drag the abdomen continuously on the ground. The recruitment trail is highly attractive: it is followed within a few seconds, by more nestmates, and at a quicker pace (on average, 6.4 mm/s) than foraging trails (on average, 2.9 mm/s). The difference between foraging and recruitment trails in R. santonensis could be attributed to different quantities of trail pheromone. A caste-specific difference in trail pheromone thresholds, with workers of R. santonensis being more sensitive to trails than soldiers, was also documented: soldiers respond only to trails with a high concentration of trail pheromone.     

Parthenogenetic reproduction in neotenics of the subterranean termite Reticulitermes speratus (Isoptera: Rhinotermitidae)

Experiments with artificial colonies consisting of only female workers and those of female nymphs and workers of a subterranean termite, Reticulitermes speratus, showed that neotenics (ergatoids and nymphoids) can reproduce parthenogenetically. The larvae hatched from the eggs produced partheno‐genetically by the neotenics were all female and did not have any aberrant external morphology. They had 42 chromosomes and were diploid. The analysis of genotypes at microsatellite loci revealed that the eggs produced parthenogenetically had only one of the two alleles that the mother neotenics possessed, indicating that the eggs were produced by automixis.     

Factors affecting mate choice in the subterranean termite Reticulitermes chinensis (Isoptera: Rhinotermitidae)

Termites are a group of eusocial insects. Mate choice is the most important step which affects the subsequent new colony foundation and development in termites. This study investigated the effects of the four factors on mate choice in the subterranean termite Reticulitermes chinensis Snyder, including colony origin, entry time, physical damage of antennae, and fresh body weights of male dealates. The results showed that the pairing number of dealates from the different colonies was significantly higher than that from the same colonies. The male dealates with early entry time achieved a significantly higher pairing number than the male dealates with late entry time. The male dealates with complete antennae achieved a the significantly higher pairing number than the male dealates lacking the six terminal segments of antennae. Moreover, the heavier male dealates achieved a significantly higher pairing number than the lighter male dealates. However, there were no significant differences in the pairing time for all the experimental treatments. These results suggested that the male dealates, which are heterogenous, healthy, heavy, and more familiar with the environment in R. chinensis, have the obvious advantages in the mate choice. This rule of mate choice is helpful for termites to avoid inbreeding and to maintain the genetic diversity of offspring, which is very important for the environmental adaptability and development of termite colonies.     

Patterns of neotenic differentiation in a subterranean termite, Reticulitermes speratus (Isoptera: Rhinotermitidae)

Plasticity in the caste developmental pathway is a remarkable characteristic of termite societies. In Reticulitermes, two types of neotenic reproductive, nymphoids and ergatoids, may differentiate from nymphs and workers and take over reproduction in the colony after the death of the original primary reproductive pair. We examined the dynamics of newly differentiated nymphoids and ergatoids in experimentally orphaned laboratory colonies of R. speratus with different caste compositions. The period required for differentiation of nymphoids was shorter than that for differentiation of ergatoids. The sex ratio of neotenics was strongly female‐biased, particularly in ergatoids. The results suggested that the number of differentiated ergatoids was restricted by the existence of nymphs or nymphoids in a colony. Workers were assumed to kill most newly differentiated neotenics. Attack reflecting conflict between colony members is probably an important mechanism to control neotenic emergence.     

Ultrastructural ontogeny of the labial gland apparatus in termite Prorhinotermes simplex (Isoptera, Rhinotermitidae)

The labial glands in Prorhinotermes simplex consist of secretory cells organized into acini, water sacs and the ducts connecting the gland parts to the basis of the labium. Acini are composed of central and parietal cells. Central cells type I contain predominantly lucent vacuoles and are involved probably in hydroquinone production. They are lacking in soldiers. Type II central cells produce vacuoles of proteinaceous content which are of the same electron density (type IIa) or present in more shades (type IIb). Type IIa cells are present in all older individuals, whereas type IIb are lacking in soldiers and neotenics. Type III cells represent a specific stage of type I cells development, but they are definite functional secretory cells in soldiers. Acini of first instar larvae contain undifferentiated cells which differentiate into type I cells during the second instar. Specific larval central cells start to change into type II cells during first instar. The central cells of presoldiers show a transition from the pseudergate into the soldier situation. The parietal cells keep a uniform structure throughout the whole ontogeny. Only one type of cells form the water sacs in all castes. The cells are very flat with scarce organelles. The water sac cells produce lipid-like secretion, small lucent vacuoles and bunches of angulated vacuoles. The water sac probably functions as water storage organ only. Ontogenetical changes in water sac development are small. The acinar ducts originate inside the acinus where they are formed by flat cells with rare organelles. At the acinus border, cells equipped with mitochondria, microvilli and basal invaginations appear. The water sac ducts are formed by flat cells with rare organelles. Acinar ducts outside the acinus and water sac ducts are equipped with taenidiuam.     

黑胸散白蚁下唇腺的解剖和扫描电镜观察

【目的】通过研究黑胸散白蚁Reticulitermes chinensis下唇腺解剖构造及其在不同品级个体间的分化,为进一步探索口交哺和品级分化机制提供参考。【方法】通过显微解剖观察,了解黑胸散白蚁下唇腺的形态构造及其在不同品级个体间的分化;通过扫描电镜观察,了解下唇腺的结构及神经支配;通过饮水实验,研究工蚁饮水及下唇腺囊的贮水功能。【结果】黑胸散白蚁下唇腺是左右对称结构,每侧构造由一个下唇腺腺泡群、一个下唇腺囊及相关的导管组成。每侧导管分别开口于舌基部下方。蚁后的下唇腺最发达,在下唇腺大小、下唇腺囊大小、腺泡大小及腺泡数量4方面均显著高于其他品级个体;兵蚁、工蚁、有翅成虫的下唇腺也较为发达,相互之间这4个参数的差异性不显著。扫描电镜观察发现,工蚁下唇腺腺泡由主导管和分支导管相连,腺泡外侧有神经分布。黑胸散白蚁工蚁有饮水习性,获得的水贮存在下唇腺囊内。【结论】黑胸散白蚁不同品级个体间,蚁后的下唇腺最发达,有翅成虫的下唇腺也比较发达,说明蚁后除行使生殖职能外,还承担交哺育幼等职能。黑胸散白蚁工蚁有饮水习性,下唇腺囊有贮水功能。     

Distribution of Formosan subterranean termite (Isoptera: Rhinotermitidae) in Mississippi

An extensive monitoring and survey program in Mississippi was conducted from 2000 to 2004 to investigate the distribution of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Seventy-two towns from 22 counties in southern Mississippi were monitored with a total of 3914 traps that catch alates during the swarming season. In addition, 259 licensed pest management professionals in Mississippi were surveyed to determine the locations of termite infestations treated. The alates of C. formosanus were recovered in 12 counties with light traps, and termite infestations were documented in an additional 13 from data collected in the termite survey. Infestations of C. formosanus have been documented in urban, urban cluster, rural, and forested areas of Mississippi. However, the distribution in mean total capture of alates for 4 yr differed significantly among the four ecological areas with the highest percentage in forested areas (31%) and the lowest percentage in urban cluster areas (17%). Most of the infestations of C. formosanus were geographically distributed along the coastal areas of southern Mississippi from Gulfport to Pascagoula. The greatest total number of alates captured in light traps was documented in Pearl River County. Mass swarming of C. formosanus occurred primarily in May or June, depending on weather conditions. The number of documented counties with the evidence of large and widely dispersed swarms of C. formosanus in different ecological areas, and the increase in total annual alate captures from 2000 to 2003, suggest that this invasive termite species is now firmly established in Mississippi.     

Effects of sublethal exposure to imidacloprid on subsequent behavior of subterranean termite Reticulitermes virginicus (Isoptera: Rhinotermitidae)

Experiments were conducted to determine whether subterranean termites, Reticuliternes virginicus (Banks), previously exposed to sublethal doses of imidacloprid (Premise), and allowed to recover for 1 wk, demonstrated behavioral aversion to a subsequent exposure. Worker termites experiencing a previous sublethal but debilitating exposure to imidacloprid-treated sand (either 10 or 100 ppm for 4 h) showed no apparent aversion to a second encounter with imidacloprid-treated sand under conditions of this experiment. If these laboratory results hold in the field and termites traveling through a zone of soil treated with imidacloprid are impaired but subsequently recover, they will be just as likely as their naive nestmates to reenter the treated area if their travels take them through the nonrepellent application a second time. Our results also indicate that a sublethal exposure to imidacloprid can affect termite tunneling behavior. Many worker termites that received an initial 4-h exposure to 100 ppm imidacloprid-treated sand died, but those that survived tunneled significantly less than did their naive nestmates, as did some termites exposed to 10 ppm imidacloprid.     

Interaction between the subterranean termite Reticulitermes flavipes (Isoptera: Rhinotermitidae) and the entomopathogenic fungus Metarhizium anisopliae in foraging arenas

The entomopathogenic fungus Metarhizium anisopliae (Metsch.) Sorokin was tested in the laboratory against field-collected groups of eastern subterranean termite, Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae), in foraging arenas to determine the potential effect of a "trap and treat" protocol (trapping a part of the population, treating it with a biological control agent and releasing it back into the original population). Individual termites were treated with a suspension of M. anisopliae conidia and released back into the arenas containing untreated termites. After 5 d, 90% of the treated termites died in the arena, but untreated termites did not exhibit a significant increase in mortality within 90 d after release, indicating no transfer of viable M. anisopliae and no epizootic. Although M. anisopliae was isolated from the arenas after 90 d, the average number of fungal colony-forming units recovered was <0.1% of the conidia introduced.     

Formosan subterranean termite swarming behavior and alate sex-ratio (Isoptera: Rhinotermitidae)

Summary The Formosan subterranean termite (Coptotermes formosanus Shiraki) was first sighted in the cities of New Orleans and Lake Charles, Louisiana, in 1966. Its distribution in the historic French Quarter of New Orleans 23 years later (1989) and in 1991 and 1992 is reported here using counts of alates from light-traps. Light-trappings revealed a Quarter-wide distribution of the termite.C. formosanus shows an extended pause in flight behavior in the middle of the two-month flight season that is predictable and independent of weather. A colony-level mechanism, namely, developmental inhibition of nymphs by alates, may regulate this intermission in flight. The sex-ratio of light-trapped alates varies over time, but is generally female-biased, especially at the height of the flight season.     

Effect of nutritional condition on larval food requisition behavior in a subterranean termite Reticulitermes speratus (Isoptera: Rhinotermitidae)

Although optimal investment theory would be similarly applicable to eusocial insects to maximize colony reproductive outputs, directly distinguishing an amount of investment in each larva should be a difficult task for workers because of the characteristics of group living. Thus, it is expected that workers adjust brood care by using a cue or signal conveying information of larval status. In termites, which are typical group of eusocial insects, there are nevertheless few direct observations on worker brood care and little is known about cues inducing worker feeding. I show here that a Japanese subterranean termite Reticulitermes speratus uses an overt food solicitation by larva, “pecking”, as a cue for worker feeding. Direct observations demonstrated that workers feed larvae in response to larval pecking. Furthermore, nutritional experiments showed that larvae exhibited pecking more frequently when their nutrient status is lower; hence, pecking may be an honest reflection of larval hunger status. These results indicate that workers can feed more starved larvae than less starved ones because pecking honestly reflects larval hunger state. That is, feeding in response to pecking should standardize the total amount of food intake of each larva and help a termite colony make worker investment efficient.     

Resistance of insecticide-treated foam board insulation against the eastern subterranean termite and the Formosan subterranean termite (Isoptera: Rhinotermitidae)

Three foam board types, one untreated control, one containing 2,000 ppm disodium octaborate tetrahydrate (DOT), and one containing 1,000 ppm deltamethrin, were exposed to field populations of the eastern subterranean termite, Reticulitermes flavipes (Kollar), and the Formosan subterranean termite, Coptotermes formosanus Shiraki. There was no significant difference in termite damage between foam boards treated with 2,000 ppm DOT and the untreated control. Form boards containing 1,000 ppm deltamethrin were not damaged by R. flavipes, whereas only minor damage occurred after exposure to C. formosanus.     

Feeding, uptake, and utilization of carbohydrates by western subterranean termite (Isoptera: Rhinotermitidae)

Western subterranean termite, Reticulitermes hesperus (Banks), prefers various mono-, di-, and trisaccharides, total feeding being the greatest on paper disks treated with 5% ribose followed by 3% xylose, 2% maltose, 2% fructose, 2% arabinose, and 2% ribose. In multiple choice tests, termites were not able to discriminate between 2% ribose, 2% fructose, 2% xylose, and 2% maltose. Termites readily take up [14C] sucrose in feeding studies. Most of the sucrose is used as an energy source for respiration (89.2%), a very small proportion remains within the termite (9.3%), and an even smaller amount is excreted as solid waste (1.5%). The amount of 14C label transferred to other colony members via trophallaxis, body contact, or grooming is small and directly dependent upon the time and numbers of donors and recipients. At day 15 postmixing, the percentage of transfer was highest, 14.4 and 15.1% for both 1:1 and 2:1 donor to recipient mixing ratios, respectively. The mean amount of labeled 14C received by recipients increased from seven disintegrations per minute (dpm) on day 2 to 30 dpm on day 15 for 1:1. Overall mean radioactivity recovered from recipient termites when mixed with donor termites at 1:1 ratio (20 dpm) was significantly less than (28 dpm) when mixed with donor termites at 2:1 ratio. Sugars act as phagostimulants to the termites at concentrations much higher to those that termites naturally encounter in wood. Termites readily metabolize carbohydrates such as sucrose, and thus their use in bait matrices may increase consumption and retention at bait stations.     

Comparison of the spatial distribution and reproductive cycle of Reticulitermes santonensis Feytaud and Reticulitermes lucifugus grassei Clément (Isoptera, Rhinotermitidae) suggests that they represent introduced and native species, respectively

Summary: The termites Reticulitermes santonensis (Rs) and R. lucifugus (Rl) were first regarded as different species (Feytaud, 1924) and then as the same species (Buchli, 1958). In later studies, Clément (1978, 1986) and Bagnères et al. (1990) used morphological and chemical (cuticular hydrocarbons) criteria to show that they actually are two distinct species. Feytaud (1924) and Bagnères et al. (1990) suggested that Rs could have originated from a North American population of R. flavipes that was introduced into Europe. The present study examined the distribution and reproductive cycle of Rs and an Rl sup-species, Rl grassei (Rlg), which are partly sympatric in southwest France. In the wild, Rs has an aggregated distribution related to human surroundings (past or present), i.e. populations are either dense or entirely absent. Conversely, Rlg is distributed randomly (from dense to few) throughout its range. For example, Rs is not found in towns within the Landes Forest, an area in southwest France that remained economically depressed and sparsely settled until after 1850 (Sargos, 1997), while Rlg is quite common there. Their respective reproductive strategies show that Rs populations spread through budding (swarms are scarce and many brachypterous nymphs and neotenics are found), whereas Rlg populations reproduce by both swarming and budding. It is likely that Rs is an introduced species and Rlg a native one that has reached its northern limits in France. A closer examination of North American Reticulitermes species, particularly R. flavipes, might reveal a relationship with the European species.