Chemical variation in defensive secretions of four species of Nasutitermes

Nineteen monoterpenes and 13 diterpenes were distinguished in soldier defensive secretions of four species of Nasutitermes. Samples of N. columbicus, N. corniger, N. ephratae and N. nigriceps were collected in Costa Rica and Panama. Interspecifically, these species can be differentiated by monoterpenes, which exhibit a complex pattern. Intraspecifically, there is detectable variation in monoterpenes and diterpenes, each of which allows discrimination of four populations of N. corniger. Similarity between two Pacific populations of N. corniger from different environments, a tropical dry forest and a rainforest, suggests there is no climatic influence on chemical compositions of defensive secretions. In addition, results from Costa Rica provide evidence that the Atlantic population of N. corniger is derived from Pacific populations.     

Interspecific variation in the defence secretions of Nasutitermes soldiers

Termite soldiers of the genus Nasutitermes (Isoptera, Termitidae, Nasutitermitinae) eject a viscous, sticky defense secretion composed of non-polar monoterpene hydrocarbons and polyoxygenated diterpenes from the frontal gland. Chemical compositions are described in detail for the East African species, N. kempae and N. infuscatus, and for the Neotropical species N. ephratae. Additional comparisons with the new world species N. costalis, N. rippertii and N. octopilis are presented. The structure of a new monohydroxykempene from N. ephratae is described, and a physicochemical model for the stickiness of the glue is presented. Although the structures of the individual secretion components vary within the genus, the glue-like nature of the secretion remains essentially unchanged. Chemical analysis of soldier defense secretions may be useful in studying the systematic biology of termites.     

Intraspecific variation in soldier defense secretions of Longipeditermes longipes (Isoptera,Nasutitermitinae)

The chemical defense secretions of major and minor soldiers of 46 colonies of the free-ranging termite Longipeditermes longipes (Isoptera, Termitidae, Nasutitermitinae) were isolated and analyzed by chromatography and spectroscopy. The colonies, collected from rainforest sites in Malaysia, showed monoterpene patterns rich in pinenes and limonene but with few qualitative differences among colonies. In marked contrast, the diterpene chemistry is highly variable that includes bicyclic (secotrinervitane), tricyclic (trinervitane), tetracyclic (rippertane), and a spirotetracyclic (longipane) skeleton. This paper presents the compositional and structural diversity, and calculates genetic distances among sympatric and allopatric colonies from a single species.     

Studies on feeding and trophallaxis in the subterranean termite Odontotermes formosanus using rubidium chloride

Differences in feeding and trophallaxis among castes of the fungus‐cultivating higher subterranean termite Odontotermes formosanus Shiraki (Isoptera: Termitidae) were determined using rubidium (Rb) as a tracer. In the feeding study, workers and third instars fed directly on Rb‐treated filter paper and acquired the highest levels of Rb content. Although fifth and sixth instars obtained the Rb content over the marked level, the feeding ability of the caste was very poor. However, soldiers did not feed on Rb‐treated filter paper. In the trophallaxis study, worker, soldier, and fifth‐ and sixth‐instar recipients paired with Rb‐fed worker donors had a significantly higher Rb content than those paired with control donors. Results indicate that soldiers are completely dependent on workers for nutrition. Workers and fifth and sixth instars may obtain nutritional material from foraging workers. When third‐instar recipients were paired with Rb‐fed worker donors, they did not have a significantly higher Rb content than when they were paired with control donors, suggesting that the frequency of worker/third instar trophallaxis was very low. Transfer efficiency from the four trophallactic combinations ranged from 1.2 (worker donors to third‐instar recipients) to 12.9% (worker donors to soldier recipients). Accordingly, nutritional material from foraging workers could be transferred to non‐foraging workers, soldiers, and fifth and sixth instars by trophallaxis; however, third instars rarely obtain nutritional material from foraging workers, because they are capable of feeding within the nest.     

Colour variation and polyethism of the soldier caste in the termite Macrotermes bellicosus

Based on abdominal colour three categories of major soldiers were found in Macrotermes bellicosus (Smeathman) (Isoptera: Termitidae). The three main colour types, yellow, red and brown are due to the colour of the defence-secretion stored in the labial gland's reservoirs. The order of these categories correlates with the uric acid titres of the whole individuals. It is concluded that colour could be used as a label for the relative age of a soldier. Age dependent polyethism was observed in soldiers: the individuals of the highest age class were the only ones leaving the nest to accompany the foraging workers, whereas all age categories were found inside the nest. After a significant loss of old individuals younger individuals show flexibility by replacing the missing outgoing nestmates. Caste regulation takes place by an increased rate of soldier development.     

Development of non-reproductive castes in the neotropical termite generaCornitermes,Embiratermes andRhynchotermes (Isoptera,Nasutitermitinae)

Summary The developmental pattern of the neuter castes was studied in the mandibulate nasute generaCornitermes, Embiratermes andRhynchotermes. InCornitermes walkeri, all the workers and soldiers are male. There are two larval and a single worker instar. Workers can molt into presoldiers. InEmbiratermes chagresi andRhynchotermes perarmatus, both sexes are present among the neuters. A slight sexual dimorphism (males > females) is discernible among both larval instars and among workers ofE. chagresi; female workers can molt into presoldiers. InR. perarmatus, the sexual dimorphism is conspicuous from the first larval instar on. Male larvae go through two instars, then give rise to workers, which do not molt. InR. perarmatus, there is no worker stage in females, but a third larval instar, preceding the presoldier. Hypotheses are proposed as to the evolution of these caste patterns, attempting to conciliate present knowledge of Nasutitermitinae phylogeny and known evolutionary trends affecting termite caste patterns, according to the species' ecology.Research Associate: National Fund for Scientific Research (Belgium).     

弯齿琵甲防御分泌物的化学成分测定及抗菌活性分析

弯齿琵甲Blaps femoralis Fischervon Waldheim是中国北方的优势土壤昆虫,其防御腺分泌物用于御敌和引起本种群体的集结,体外具有一定毒性,民间将该虫作为药用昆虫资源利用年代久远。由该虫防御腺体获得分泌物并经气相色谱-质谱联用技术(GC-MS)分析,共计获得14种小分子化合物,其中以2-甲基苯醌、1-十三碳烯和2,4-二甲基-3-呋喃乙酮含量较高,苯醌、苯二酚、3,5-二羟基甲苯和十二烷醛等小分子化合物次之。研究证实该分泌物具有较明显的抑菌能力。研究结果为今后进一步深入开展弯齿琵甲的防御腺化学分泌物天然产物的研究积累了工作。     

Microsatellite loci in the Japanese subterranean termite,Reticulitermes speratus

Reticulitermes termites have such a cryptic life style and complex colony structure that polymorphic microsatellite markers are desired to investigate their population and colony structures. We successfully isolated seven microsatellite loci in R. speratus , the Japanese subterranean termite, five of which were polymorphic. These polymorphic loci had 2–8 alleles per locus and their observed heterozygosities ranged from 0.059 to 0.438. These five loci were also polymorphic in R . kanmonensis , distributed sympatrically with R. speratus in the Kanmon Region, western Japan; the number of alleles per locus was 2–5, and observed heterozygosity was 0.176–0.625.     

Isolation and characterization of 10 microsatellite loci in the magnetic termite,Amitermes meridionalis (Isoptera: Termitidae)

The elongated mounds of the ‘magnetic termite’, Amitermes meridionalis are a prominent feature of the Northern Territory in Australia. They are restricted to habitat patches of seasonally flooded plains which are largely isolated from each other. To investigate the population structure of A. meridionalis, we developed 10 polymorphic microsatellite loci. We tested the variability of the markers on at least 20 individuals from two populations. We found three to 12 alleles per locus with a level of heterozygosity at each locus ranging from 0.05 to 0.74.     

尖唇散白蚁工蚁、兵蚁和繁殖蚁精子发生的比较研究

为探讨白蚁非生殖品级和生殖品级生殖细胞发育差异,采用组织学染色技术对尖唇散白蚁Reticulitermes aculabialis Tsaiet Hwang繁殖蚁、工蚁和兵蚁的精巢发育以及精子发生进行了显微观察和比较研究。结果发现3个品级间精巢发育的程度差异很大,三者精巢切面面积相对大小之比为:繁殖蚁∶工蚁=1.7∶1;繁殖蚁∶兵蚁=29.3∶1;工蚁∶兵蚁=17.1∶1。繁殖蚁和工蚁精巢管内有精子的形成,工蚁和繁殖蚁精子的发生都经历了精原细胞、初级精母细胞、次级精母细胞、精细胞和精子时期,但工蚁有大量次级精母细胞呈细胞凋亡状态。兵蚁生殖细胞发育仅有精原细胞、初级精母细胞、次级精母细胞,没有精细胞和精子产生。工蚁的生殖细胞显著小于同一时期繁殖蚁的生殖细胞,兵蚁的各时期生殖细胞均极显著小于繁殖蚁同一时期的生殖细胞。研究表明各品级之间生殖功能分化与生殖细胞发育有直接关系,工蚁有转化为补充繁殖蚁和兵蚁的能力;而兵蚁由于精巢极度退化不能产生精细胞和精子,因此是非生殖品级分化的终极形式,不具有转化成补充繁殖蚁或其它品级的能力。     

Chemical constituents of tropical woods and resistance to the invasive drywood termite Cryptotermes brevis

Wood-feeding, nesting and production of secondary reproductives are key determinant traits of invasive species of drywood termites, and the West Indian drywood termite Cryptotermes brevis (Walker) is one of their major examples of worldwide concern as pest species of structural lumber, furniture and other wood products. The problem and losses by this species are determined by the prevailing wood characteristics. However, despite the current widespread occurrence of this species in the tropics, except Asia, tropical wood resistance and underlying mechanisms of resistance against this termite are scarcely known. Nonetheless, wood hardness and particularly wood density were recently recognized as important underlying traits for C. brevis resistance in tropical woods, but the chemical wood constituents were not considered. Here, we assessed tropical wood resistance to the invasive termite species C. brevis and tested the relevance of their holocellulose, lignin and (total) extractive contents preventing termite infestation. Free-choice and no-choice tests were carried out in parallel with wood chemical characterization. Resistance to the West Indian termite varied with wood species in terms of both colonization and consumption, but only under free-choice testing because without choice, no significant difference was detected among wood species. Regardless, none of these traits were significantly correlated with wood resistance to C. brevis. Therefore, wood physical resistance, particularly wood density, seems the main recognized determinant of tropical wood resistance against the West Indian drywood termite. The pattern of termite movement on the surface of soft, mid and hard wood was also consistent with this conclusion.     

Colony and population genetic structure of the Formosan subterranean termite,Coptotermes formosanus,in Japan

Subterranean termites have unusual plasticity in their breeding systems. As a result of their cryptic foraging and nesting habits, detailed information on the numbers and types of reproductive individuals in colonies has been difficult to obtain. In this study, we used microsatellite markers to infer the major features of the breeding system of the Formosan subterranean termite, Coptotermes formosanus, in southern Japan, where it is believed to have been introduced from China. A total of 30 colonies was sampled from two islands (Kyushu and Fukue) located 100 km apart. Twenty workers from each colony were genotyped at six microsatellite loci. Analysis of worker genotypes within colonies indicated that 27 colonies (90%) were simple (Mendelian) families. The remaining three colonies, all from Kyushu, were consistent with being extended families having begun as simple families but being currently headed by multiple neotenic (secondary) reproductives descended from the original king and queen. Workers from simple families in both populations were significantly inbred (FIT = 0.10 for Kyushu and 0.46 for Fukue) and highly related to their nestmates (coefficient of relatedness, r = 0.59 for Kyushu and 0.77 for Fukue), suggesting that many simple-family colonies were headed by closely related reproductives, especially in the Fukue population. This conclusion is supported by the high coefficient of relatedness between nestmate reproductives in simple-family colonies (r = 0.23 for Kyushu and 0.61 for Fukue) based on genotypes inferred from their worker offspring. There was moderate genetic differentiation (FST = 0.12) between the two populations, suggesting rather restricted gene flow between them. There was no significant isolation by distance among colonies, as might be expected given the limited dispersal of reproductives, presumably because of the frequent movement of colonies by humans. Finally, there was no evidence of a recent bottleneck, a finding possibly consistent with the more than 300-year history of this species in Japan.     

Queen replacement in the termiteMicrocerotermes papuanus

In experimentally orphaned field nests ofMicrocerotermes papuanus Holmgren, 1911, large numbers of workers develop into replacement reproductives (ergatoids) in only one moult. The females become functional egg-layers after approximately two months. Nymphs normally reach the last instars in August–September; at that time, in the orphaned nests, some nymphs moult to nymphoid replacement reproductives. Over long time periods, these nymphoids completely replace the ergatoids and the females become physogastric. Although time-efficient, queen replacement seems energetically expensive for the society, suggesting that this process is under weak selective pressure inM. papuanus, compared with sympatric species such asNasutitermes princeps.

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Le remplacement de la reine chez le termiteMicrocerotermes papuanus

Résumé Dans les nids deM. papuanus rendus expérimentalement orphelins, un grand nombre d'ouvriers se transforment, en une seule mue, en sexués de remplacement ergatoïdes. Les femelles se mettent à pondre au bout d'environ deux mois. Les nymphes atteignent normalement leurs derniers stades en août-septembre. A ce moment, dans les nids orphelins, certaines d'entre elles se différencient en sexués nymphoïdes. Dans les expériences de longue durée, ces nymphoïdes remplacent complètement les ergatoïdes et les femelles deviennent physogastres. Bien que rapide, le remplacement de la reine paraît coûteux pour la société du fait du grand nombre d'individus, ouvriers et nymphes, impliqués. Ceci suggère que la pression de sélection sur ce phénomène est faible chezM. papuanus, par comparaison avec des espèces sympatriques telles queN. princeps.

     

Minimizing moving distance in deposition behavior of the subterranean termite

Subterranean termite nests are located underground and termites forage out by constructing tunnels to reach food resources, and tunneling behavior is critical in order to maximize the foraging efficiency. Excavation, transportation, and deposition behavior are involved in the tunneling, and termites have to move back and forth to do this. Although there are three sequential behaviors, excavation has been the focus of most previous studies. In this study, we investigated the deposition behavior of the Formosan subterranean termite, Coptotermes formosanus Shiraki, in experimental arenas having different widths (2, 3, and 4 mm), and characterized the function of deposited particles. We also simulated moving distance of the termites in different functions. Our results showed that total amounts of deposited particles were significantly higher in broad (4 mm width) than narrow (2 mm) tunnels and most deposited particles were observed near the tip of the tunnel regardless of tunnel widths. In addition, we found that deposited particles followed a quadratic decrease function, and simulation results showed that moving distance of termites in this function was the shortest. The quadratic decrease function of deposited particles in both experiment and simulation suggested that short moving distance in the decrease quadratic function is a strategy to minimize moving distance during the deposition behavior.     

Ability of bed bug (Hemiptera: Cimicidae) defensive secretions (E)‐2‐hexenal and (E)‐2‐octenal to attract adults of the common bed bug Cimex lectularius

Accurate and timely surveillance of bed bug infestations is critical for the development of effective control strategies. Although the bed bug‐produced volatiles (E)‐2‐hexenal and (E)‐2‐octenal are considered as defensive secretions, the present study demonstrates, using ethovision® video‐tracking software (Noldus Information Technology Inc., Leesburg, Virginia), that low amounts of these commercially‐obtained aldehydes function as attractants, and high amounts function as local repellents, against the common bed bug Cimex lectularius L. In behavioural assays, both males and female C. lectularius are attracted to 0.04 µg of an aldehyde blend (1 : 1) for up to 1 h after initial treatment of filter paper disks. Males differ from females in their response to higher amounts of aldehydes, with females and males exhibiting maximum local repellency at 40 µg and 400 µg, respectively. The results suggest that these bed bug secretions may be candidates for lures and monitors.     

Regulation of juvenile hormone titers by soldiers in the Formosan subterranean termite, Coptotermes formosanus

In field collections of the Formosan subterranean termite Coptotermes formosanus, soldiers averaged less than 10%. The proportion of soldiers increased to about 25% or higher when termites were kept in the laboratory, as did the juvenile hormone III (JH III) titers for both workers and soldiers. In laboratory experiments with a proportion of soldiers 25% or higher, very few new pre-soldiers were formed and the JH titer in existing soldiers remained constant. On the contrary, workers from groups containing less than 25% soldiers formed more pre-soldiers. In such cases, both workers and soldiers showed higher JH titers. Newly formed soldiers also had higher JH titers than older soldiers. It is speculated that populations containing higher soldier proportions inhibit further soldier differentiation, eventually holding the JH titers under the threshold or suppressing the activity of corpora allata resulting in lower JH titers in workers.     

黄粉虫防御性分泌物化学成分的GC/MS分析

用二氯甲烷为溶剂萃取黄粉虫成虫腹部防御性分泌物并经GC/MS法分析,检测出其中7种成分:2-甲基对苯醌、对甲酚、正二十三烷、正二十四烷、12-二十五烯、正二十五烷和正二十六烷。幼虫和蛹腹末端的体液与成虫防御性分泌物共有4种长链烷烃,幼虫另含有3种有机酸。幼虫和蛹均不含有毒性较强的2-甲基对苯醌和对甲酚,用作动物蛋白饲料较安全。对成虫分泌物中的2-甲基对苯醌和对甲酚进行了定量分析,并探讨了不同日龄和性别的成虫防御性分泌物的分泌规律及再生性特点。     

Genetic analysis of the breeding system of an invasive subterranean termite, Reticulitermes santonensis, in urban and natural habitats

Reticulitermes santonensis is a subterranean termite that invades urban areas in France and elsewhere where it causes damage to human-built structures. We investigated the breeding system, colony and population genetic structure, and mode of dispersal of two French populations of R. santonensis. Termite workers were sampled from 43 and 31 collection points, respectively, from a natural population in west-central France (in and around the island of Oleron) and an urban population (Paris). Ten to 20 workers per collection point were genotyped at nine variable microsatellite loci to determine colony identity and to infer colony breeding structure. There was a total of 26 colonies, some of which were spatially expansive, extending up to 320 linear metres. Altogether, the analysis of genotype distribution, F-statistics and relatedness coefficients suggested that all colonies were extended families headed by numerous neotenics (nonwinged precocious reproductives) probably descended from pairs of primary (winged) reproductives. Isolation by distance among collection points within two large colonies from both populations suggested spatially separated reproductive centres with restricted movement of workers and neotenics. There was a moderate level of genetic differentiation (F(ST) = 0.10) between the Oleron and Paris populations, and the number of alleles was significantly higher in Oleron than in Paris, as expected if the Paris population went through bottlenecks when it was introduced from western France. We hypothesize that the diverse and flexible breeding systems found in subterranean termites pre-adapt them to invade new or marginal habitats. Considering that R. santonensis may be an introduced population of the North American species R. flavipes, a breeding system consisting primarily of extended family colonies containing many neotenic reproductives may facilitate human-mediated spread and establishment of R. santonensis in urban areas with harsh climates.     

Harvesting rate of the termite,Drepanotermes tamminensis (Hill) within native woodland and shrubland of the Western Australian wheatbelt

The Western Australian termite,Drepanotermes tamminensis (Hill), harvests various plant materials according to biomass availability. The main litter components harvested by this termite in a woodland dominated byEucalyptus capillosa are bark and leaves of the major tree species, while in shrubland dominated byAllocasuarina campestris, shoots of this species are taken. Harvesting mainly occurs during the autumn (April–May) and spring (September–October) seasons. The commencement and duration of harvesting appears to depend partly on weather conditions, with harvesting taking place at temperatures between 15 and 25°C after periods of rain. This species of termite harvests approximately 15.6 g m⁻² year⁻¹ and 3.2 g m² year⁻¹ (dry weight of plant material) in the woodland and shrubland, respectively.