Estimating termite population size using spatial statistics for termite tunnel patterns

Subterranean termites build underground tunnels for foraging. The obtained food is transported to the nest through these tunnels, and consumed to maintain the termite colony. In this process, termites can cause damage to wooden structures. To develop effective control strategies to reduce termite damage, it is important to know the sizes of the termite populations in the tunnels. In this study, we proposed a method for estimating the termite population size using the spatial statistic indices including fractal dimension (FD), local density (LD), and join count statistic (JCS) for the tunnel patterns. However, the method needs further improvement to be applied in field conditions. For the method, we generated 8,000 tunnel pattern images (1,000 images for each N) using an agent-based model based on experimental data. Here, N (= 3, 4, ..., 10) represents the number of termites participating in tunnel construction in the simulation. Subsequently, we calculated the FD, LD and JCS values of the tunnel pattern and trained and verified the k-nearest neighbors (KNN) algorithm, using 5,600 and 2,400 images, respectively. The population size (N) was estimated based on the FD, LD and JCS using the KNN algorithm. The estimated accuracy for all N was 60% to 97% in the range of k = 1 to 300. If the model for tunnel pattern generation includes heterogeneous environmental conditions, the proposed method could be used to effectively estimate the actual number of termite populations. Finally, we briefly discuss the challenges affecting our model, and how these could be overcome.     

白蚁信息素研究进展

白蚁是最古老的社会性昆虫, 其社会性的维持需要信息素的相互作用。本文回顾了近年来国内外白蚁信息素研究的最新进展, 内容涉及白蚁踪迹信息素、 性信息素、 告警信息素和促食信息素的功能、 化学成分及产生信息素的外分泌腺。白蚁分泌信息素的腺体主要有背板腺、 腹板腺、 后腹板腺、 额腺和唾腺。绝大多数白蚁信息素是挥发性物质。白蚁在化学通讯上存在节俭策略, 即同一种化合物由不同的白蚁种类的不同外分泌腺分泌, 可具有不同的功能。总结了各类信息素在白蚁物种间、 同一物种的品级间和性别间的异同和作用方式, 强调了白蚁信息素的反应阈值、 最佳浓度、 有效期和物种特异性对其功能的影响。目前对白蚁信息素的研究尚处于起步阶段, 其研究成果对等翅目系统发育研究和白蚁防治具有重要的意义。文章最后展望了白蚁信息素在白蚁防治上的应用前景。     

Symbiosis of a termite and a sclerotium-forming fungus: Sclerotia mimic termite eggs

Brown balls, of a similar size but different shape to termite eggs, were found frequently in the piles of eggs of the subterranean termite Reticulitermes speratus. rDNA analysis identified the ball as the sclerotia of the fungus, Fibularhizoctonia sp. nov, which is phylogenetically closest to decay fungi, Athelia spp. Laboratory observation showed that the workers gathered the eggs and the sclerotia indiscriminately, even if they were widely scattered in a Petri dish, and piled them up in a specific place for egg care. We compared the morphology of the eggs with that of sclerotia of Fibularhizoctonia spp. and Athelia spp. in relation to egg carrying behaviour, and found that the workers could only carry the Fibularhizoctonia spp. sclerotia whose diameters were similar to the short diameter of the eggs. We also conducted a bioassay using termite eggs and dummy eggs (glass beads and sea sand) of two diameter-classes, coated with or without the egg-derived chemicals. The workers recognized the eggs based on a combination of the size, shape, and chemical cues. All the results suggested that the sclerotia mimic the eggs both morphologically and chemically. Finally, we found that the workers suppressed germination of sclerotia, and termite egg survival increased in the presence of sclerotia only if they were tended by the workers. If the workers were removed experimentally, the sclerotia germinated and grew by exploiting termite eggs. These results suggest that the sclerotia protect termite eggs from putative pathogens.     

Egg care by termite soldiers

The handling and transportation of eggs by soldiers of Prorhinotermes simplex after a nest disturbance is described. The soldiers, apart from performing alarm and defensive activities, tried to handle the eggs on the open surface. They often succeeded in lifting an egg or even a group of eggs, and then searched for a nest entrance. They either entered the nest to come out without the egg(s) within a while, or they passed the egg(s) onto a pseudergate waiting in the opening. As a result, all eggs were rapidly evacuated. Laboratory experimentation showed that pseudergates and nymphs try to deposit the eggs in a dark shelter, whereas the soldiers tend to transfer the eggs to nestmates and drop them after a while if no other termite accepts them. Received 25 February 2005; revised 26 April 2005; accepted 3 May 2005.     

谈谈白蚁与人类的密切关系

白蚁对人类的危害众所周知 ,白蚁对人类的有益方面 ,人们知之甚少。该文重点论述白蚁对人类有益的方面。白蚁在自然界中 ,是一个名符其实的“清道夫” ,它将林地中的枯枝、落叶等转化为有益的肥料 ,回归自然 ,再被植物吸收 ;白蚁本身可加工成营养丰富的美味佳肴食品 ,也可精制成防病治病的良药和效果明显的保健补品 ;白蚁的附生物 ,如鸡菌更是美味佳肴 ,菌圃和炭棒菌也能精制成治疗多种疾病的良药。     

Phylogenetic diversity of termite gut spirochaetes

A molecular phylogenetic analysis was done of not-yet-cultured spirochaetes inhabiting the gut of the termite, Reticulitermes flavipes (Kollar). Ninety-eight clones of near-full-length spirochaetal 16S rDNA genes were classified by ARDRA pattern and by partial sequencing. All clones grouped within the genus Treponema , and at least 21 new species of Treponema were recognized within R. flavipes alone. Analysis of 190 additional clones from guts of Coptotermes formosanus Shiraki and Zootermopsis angusticollis (Hagen), as well as published data on clones from Cryptotermes domesticus (Haviland), Mastotermes darwiniensis Froggatt, Nasutitermes lujae (Wasmann) and Reticulitermes speratus (Kolbe), revealed a similar level of novel treponemal phylogenetic diversity in these representatives of five of the seven termite families. None of the clones was closely related (i.e. all bore ≤ 91% sequence similarity) to any previously recognized treponeme. The data also revealed the existence of two major phylogenetic groups of treponemes: one containing all of the currently known isolates of Treponema and a large number of phylotypes from the human gingival crevice, but only a minority of the termite gut spirochaete clones; another containing the majority of termite spirochaete clones and two Spirochaeta ( S. caldaria and S. stenostrepta ), which, although free living, group within the genus Treponema on the basis of 16S rRNA sequence. Signature nucleotides that almost perfectly distinguished the latter group, herein referred to as the 'termite cluster', occurred at the following ( E. coli numbering) positions: 289-G · C-311; A at 812; and an inserted nucleotide at 1273. The emerging picture is that the long-recognized and striking morphological diversity of termite gut spirochaetes is paralleled by their phylogenetic diversity and may reflect substantial physiological diversity as well.     

Some Xylaria species on termite nests

Xylaria arenicola, X. brasiliensis, X. escharoidea, X. furcata, X. nigripes, X. piperiformis and X. rhizomorpha represent ancient names of fungi known to inhabit abandoned termite nests. We attempt to redescribe them and to reduce the confusion among them. Xylaria tanganyikaensis and X. readeri, species that might be associated with termite nests, are described. We describe a new variety, X. furcata var. hirsuta, and discuss an unnamed fungus that probably represents a new species. Photographs and a key are presented to aid the identification of these taxa.     

乳白蚁不同品级的比例

乳白蚁Coptotermes在湖北宜昌地区每年11月～次年3月收集到的巢群,每年品级比例基本平衡。品级头比的数据一律来自1月份的巢群;品级重比是11月～次年3月的巢群。品级的比例分别为：工蚁占81．70％、干重比69．45％;兵蚁占7．50％、干重比7．69％;生殖蚁占10．80％、干重比26．76％。     

白蚁肠道共生体的纤维素代谢体系

白蚁是大陆生态系统中木质纤维素降解的生力军,其肠道共生系统纤维素酶对纤维素的消化起到了关键的作用.本文概述了白蚁自身及其肠道共生微生物的纤维素水解系统的特点、相互关系以及相互作用的研究进展.     

Dynamics of termite populations-some theoretical considerations

Summary Various mathematical models are examined to fit the growth of termite populations. Termite populations show marked periodic fluctuations and these have their own biological significance. In the long run, notwith-standing the periodic fluctuations, the population continues to grow, if not infinitely.The intrinsic rate of population growth is dependent primarily on the fecundity of the queen. The population levels of different castes and population fluctuations are brought about by the selective development of the eggs into the adults of different castes and alates. Most of the models fail to account for the physiological and biological factors involved in termite population growth. A tentative model is suggested to express the population growth against time.Several hypotheses concerning the population regulation mechanisms of insects are examined and evaluated in relation to the termite populations. It is suggested that population growth of termites is probably regulated by homeostatic mechanisms.     

我国白蚁资源利用的现状

白蚁是世界性害虫,但白蚁资源有着很高的利用价值。文章简要论述我国白蚁资源利用的研究现状及研究进展,主要包括白蚁本身、蚁巢及菌圃、蚁巢共生物--鸡榕菌Termitomyces albuminosus(Berk.)Heim、乌灵参Xylaria nigripes等直接利用价值及白蚁活动加速自然界物质循环、改善土壤理化性质、探矿等间接利用价值。同时还对白蚁资源研究利用的前景进行了展望。     

Genetically engineered termite gut bacteria (Enterobacter cloacae) deliver and spread foreign genes in termite colonies

Indigenous gut bacteria of the Formosan subterranean termite (Coptotermes formosanus Shiraki, Isoptera: Rhinotermitidae) were used as shuttle systems to deliver, express and spread foreign genes in termite colonies. The gut bacterium Enterobacter cloacae was transformed with a recombinant plasmid (pEGFP) containing genes encoding ampicillin resistance and green fluorescent protein (GFP). In laboratory experiments, termite workers and soldiers from three colonies were fed with filter paper inoculated with transformed bacteria. Transformed bacteria were detected in termite guts by growing the entire gut flora under selective conditions and checking the cultures visually for fluorescence. We demonstrated that (1) transformed bacteria were ingested within a few hours and the GFP gene was expressed in the termite gut; (2) transformed bacteria established a persistent population in the termite gut for up to 11 weeks; (3) transformed bacteria were efficiently transferred throughout a laboratory colony, even when the donor (termites initially fed with transformed bacteria) to recipient (not fed) ratio was low; (4) transformed E. cloacae were transferred into soil; however, they did not accumulate over time and the GFP plasmid was not transferred to other soil bacteria. In the future, transgenic bacteria may be used to shuttle detrimental genes into termite colonies for improved pest control.     

The ommatidium of the termite mastotermes darwiniensis

An electron microscope study of the compound eye of the termite Mastotermes darwiniensis shows that the ommatidia have both primitive and specialized features. The ommatidia are of the apposition type with eight similar retinular cells, a fused rhabdom, irregularly orientated rhabdomere tubules and no tracheae. The retinula cells contain lipid. The cone cells have unusual processes, which thicken towards the basement membrane and contain rough endoplasmic reticulum, granules and dense bodies. These processes may act as a primitive transport system for nutrients.     

Immobilizing bifenthrin on wood for termite control

Termites are world-wide pests causing significant losses to annual and perennial crops, as well as damages to wooden components in buildings. Although various chemical, physical, and biological methods have been explored to prevent termite attack on wooden structures, new guiding principles are still needed for environmental protection. In this study, by combining the effective chemical control of bifenthrin and photo-immobilization technique of biomolecules, we developed chitosan as a carrier to embed bifenthrin, which was then immobilized by ultraviolet treatment on the surface of wood (Cunninghamia lanceolata). The immobilized bifenthrin embedded in the photoactive chitosan was characterized by Fourier transform infrared spectroscopy (FTIR), C.H.N analysis, ultraviolet, and fluorescence measurements. The surface structures and biological activity were examined by scanning electron microscopy (SEM), atomic force microscope (AFM), electron spectroscopy for chemical analysis (ESCA), and bioassays. The results indicated that the immobilized bifenthrin can be well protected from free and non-controlled releasing, and has a long-term stability allowing high efficiency against the termite at a dose of 2.5 ??g/cm². This study provides a novel and environmentally-benign technique for the termite control by photo-immobilizing the bifenthrin-embedded chitosan on the surface of C. lanceolata. This technique may be used in combination with the traditional methods for effective termite control.     

Polymorphism in the neotropical termite Serritermes serrifer

Serritermitidae (Isoptera) is a small and little known Neotropical termite family which includes only two genera: Glossotermes and Serritermes. Despite the lack of detailed studies, it has been assumed that these termites have a true worker caste. A recent study revealed that Glossotermes has a linear development pathway and lacks true workers. Here, we present a study of the polymorphism of Serritermes serrifer Hagen & Bates, a species endemic to the Cerrado ecoregion of central Brazil which lives as an inquiline inside nests of Cornitermes spp. A morphometric analysis was performed based on measurements taken of 11 body parts of 544 specimens of immatures, worker‐like individuals, soldiers, and alates. Sex of specimens was determined by dissection and examination of the seventh sternite. A principal component analysis (PCA) was used to evaluate morphological changes during development. Contrary with previous information from the literature and similar to Glossotermes, Serritermes shows a linear development pathway with two larval instars, two sizes of pseudergates, and a single nymphal morph. Pseudergates apparently undergo stationary molts. Sex ratio among pseudergates is male‐biased, but not as strongly as in Glossotermes. Typical colonies have a single physogastric primary queen and a single primary king. Ergatoid reproductives are relatively rare and some female ergatoids may become strongly physogastric. Nymphoid reproductives were not found. All soldiers are male and bear well‐developed testes.