Yoshiyuki Yanase

Feeding responses of the western dry-wood termite Incisitermes minor (Hagen) (Isoptera: Kalotermitidae) against ten commercial timbers

Five Japanese timbers, four timbers from the USA, and one Malaysian timber were evaluated for their resistance to the invasive dry-wood termite Incisitermes minor (Hagen) using laboratory choice and no-choice feeding tests with holed specimens. The highest survival rates of I. minor in both the heartwood and sapwood no-choice feeding tests were more than 70% after 3 months. When offered sapwood and heartwood choice feeding tests and the combined choice feeding tests, the highest survival rates of I. minor were more than 75% after 3 months. With regards to the percentage of wood mass losses in the no-choice and choice feeding tests, karamatsu (Larix leptolepsis), buna (Fagus crenata), and Douglas fir (Pseudotsuga menziesii) were classified as “resistant” species among the ten sapwood specimens. In the heartwood no-choice and choice feeding tests, the resistant species were buna, karamatsu, Douglas fir, sugi (Cryptomeria japonica), akamatsu (Pinus densiflora), and western red cedar (Thuja plicata). The ranking of the resistance of the ten commercial timbers against I. minor was buna > karamatsu > sugi > western red cedar > Douglas fir > rubber > western hemlock > hinoki > spruce.

X-ray tomographic analysis of the initial structure of the royal chamber and the nest-founding behavior of the drywood termite Incisitermes minor

The nesting biology of the drywood termite, Incisitermes minor, is poorly understood. To date, no published data are available regarding the in situ nest-gallery development of I. minor. Three naturally infested Sitka spruce (Picea sitchensis Bong. Carriere) timbers were analyzed by X-ray computer tomography to observe the structure of the first royal chamber and the termite’s nest-founding behavior. One timber was infested by a group of termites which emerged from their natal nest. The other two timbers were infested by dealate reproductives from the nuptial flight. The study revealed that the drywood termite engages in outside foraging activity and has great foraging flexibility. Computer tomographic images also revealed that I. minor reproductives showed anatomical selectivity in their nest-founding activity. The structure of the initial royal chambers varied to follow the anatomical texture of the timbers, which resembled either a European pear shape or a cashew nut shape.

Wood anatomical selectivity of drywood termite in the nest-gallery establishment revealed by X-ray tomography

Termite nest architecture has important biological attributes, as the whole structure represents a morphological expression of the sum of behavioral patterns which relate to a better understanding of their feeding ecology. The nest-gallery system of the western drywood termite, Incisitermes minor, inside naturally infested wood was visualized by X-ray computed tomography. Drywood termites are considered one-piece nesters; therefore, studying the anatomical properties of wood could increase the insight into those factors that influence the mechanisms used when the nest-gallery system is established. The interactions between the I. minor colony and environment, represented by the wood’s anatomical properties of fibers and growth rings, generate a distinctive and unique foraging pattern, which lead to selective excavation of the nest-gallery system. The results indicated that drywood termites exhibited continual adaptation to their environment as well as self-organization, similar traits of foraging and nesting biology can also be found in intermediate and separate nesters, however, at a different ecological scale.

Evaluation of the temperature and relative humidity preferences of the western dry-wood termite Incisitermes minor (Hagen) using acoustic emission (AE) monitoring

Twenty-four different combinations of six temperatures (15°, 20°, 25°, 30°, 35°, and 40°C) and four relative humidity (RH) (60%, 70%, 80%, and 90%) conditions were used for pseudergates of the western dry-wood termite Incisitermes minor (Hagen). The feeding activities of the termites were monitored by the detection of generated acoustic emission (AE) events from feeder wood blocks in a test chamber. Temperature and RH showed independent and interactive significant effects on the feeding activity of I. minor. The optimal temperature and RH conditions for the feeding activities were 35°C and 70%, respectively, and the optimal combinations were 35°C-70% and 35°C-80% with an exceptionally higher feeding activity at the combination condition of 30°C-70%.

Nest-Gallery Development and Caste Composition of Isolated Foraging Groups of the Drywood Termite, Incisitermes minor (Isoptera: Kalotermitidae)

An X-ray computed-tomographic examination of nest-gallery development from timbers naturally infested by foraging groups of Incisitermes minor colonies was conducted. This study documents the colonization process of I. minor to new timbers and how the isolated groups maintain their nest-gallery system. The results suggested that development of a nest-gallery within a suitable wood item is not random, but shows selection for softer substrate and other adaptations to the different timber environments. Stigmergic coordinations were expressed in dynamic changes of the nest-gallery system; indicated by fortification behavior in sealing and re-opening a tunnel approaching the outer edge of the timber, and accumulating fecal pellets in particular chambers located beneath the timber surface. The study also examines the caste composition of isolated groups to discover how I. minor sustains colonies with and without primary reproductives.

Development of Radar Apparatus for Scanning of Wooden-Wall to Evaluate Inner Structure and Bio-Degradation Non-Destructively

A nondestructive and small FMCW radar apparatus for scanning of the wooden wall to evaluate inner structure and biodegradation progressed in the wall was developed, and the performance of the apparatus was investigated. The allocations and the properties of the construction members in the wall, such as wooden posts and beams, metal plate connectors and insulating materials was recognized as 2D and 3D images. The moist area of more than 50% in moisture content in the wall was also recognized, and this suggests that the area of potentiality of biodegradation such as fungal and insect attacks in the wall can be detected by this apparatus. The feasibility of the apparatus to evaluate of the loss in the wood substance caused by the bio-degradation was also confirmed.

Application of Particulate Materials to a Physical Barrier against Termites-Effects of Size, Shape and Surface Properties of Particles on the Penetration Behavior of Termites-

1 緒 言 内分泌攪乱化学物質やダイオキシン汚染が明るみに出 て,農薬や化学物質の濫用に少しでも歯止めをかけよう という動きが世界的に高まってきている.さらに住宅に 関連するシックハウス症候群に対する懸念も高まる中, シロアリ防除業界もそのような動きに無関係でいること はできず,最近ではレスケミカル(省薬施工)やケミカ ルフリー工法という新しい防除技術の開発が期待されて いる.すでにアメリカなどでは,次世代の防除法の実験 や実用化が進んでいる中,わが国でも日本の風土,建築 様式にあった防除技術の確立が必要になってくる.薬 剤を使わずにシロアリの侵入を阻止する方法には,ア メリカの BTB®(玄武岩の破砕物),1)オーストラリアの Granitgard®(花崗岩の破砕物)2)に代表される岩石破砕物 や小石などの粒子を用いた物理バリア工法がある.これ は,ある一定の粒子径範囲をもった粒子を層状に用いる ことで,地下からのシロアリの侵入を防ぐ工法である. これまで,様々な粒子を用いて,地下シロアリの侵入に 対する物理バリア層の効果が検討されてきたが,砂や火 山灰を用いた物理バリア層では,1.2~ 1.7mmの粒子か らなるバリア層が貫通を阻害したという結果が最初に報 告され,3)粒子を用いた物理バリアが化学防除の代替とな りうる可能性が示された.また,石英と化石サンゴから なる砂粒を用いてガラス管内に物理バリア層を作り,イ エシロアリと西欧の地下シロアリである Reticulitermes flavipes (KOLLAR) について試験した結果,イエシロア リでは 1.70~ 2.80mm,R. fravipesでは 1.00~ 2.36mm の粒子が貫通を阻止すること,貫通を阻止した粒子径範 囲よりも小さい粒子は,シロアリの口器で運搬され,大 きい粒子は粒子どうしの隙間を通り抜けられ,バリア層 が貫通されることがわかった.4)そのほか,様々な粒子材 料と地下シロアリ種との組み合わせで,物理バリア層の 種々の粒子材料のシロアリ物理バリアへの適用 ―粒子径,粒子形状および表面性状がシロアリの貫通行動に与える影響― 簗 瀬 佳 之 藤 井 義 久 奥 村 正 悟 吉 村 剛 今 村 祐 嗣 石 田 充 克 川 口 浩 寿 奥 村 敏 信 石 田 充 克 Application of Particulate Materials to a Physical Barrier against Termites ― Effects of Size, Shape and Surface Properties of Particles on the Penetration Behavior of Termites―

Plate-type waveguides for detecting acoustic emissions generated by termite attacks

To examine the feasibility of using plate-type waveguides for effective detection of acoustic emissions (AEs) from termite attacks in wood, AEs generated by breaking pencil leads or by termite attacks were detected using an AE sensor with a resonant frequency of 140kHz with steel plates of four different sizes and thickness and three AE sensors without them. The larger plates were associated with larger amplitudes of the artificial AEs. The amplitudes of AEs detected by an AE sensor with a steel plate larger than 30×30mm were greater than the average amplitude of the artificial AEs detected by three AE sensors. When detecting AEs generated by the feeding activity of workers,Coptotermes formosanus Shiraki, the cumulative AE events detected by the sensor with a steel plate were much larger than those of the three AE sensors without a plate. Because AE waves are attenuated much less in a steel plate than in wood, it is more effective to attach the AE sensor to wood with a steel plate rather than directly to the wood. These findings suggest that it is feasible to use an AE sensor with a plate-type waveguide for the nondestructive detection of termite attacks in wood.

Volume Visualization of Hidden Gallery System of Drywood Termite Using Computed Tomography: A New Approach on Monitoring of Termite Infestation

In recent years, X-ray computed tomography (CT) has been developed as a reliable indirect method for insect studies. Here, we introduce the 3D volume visualization of hidden gallery system of drywood termites using computed tomography. Structural timbers infested by the western drywood termite, Incisitermes minor, with various dimensions were subjected into X-ray CT scanning analysis. The tomographic data were reconstructed by direct volume rendering using a volume graphic application. By rendering the tomographic data set, timber properties such as springwood, summerwood, and knots are able to be characterized; and by further specifying the opacity area, the nest-gallery systems inside the timbers are able to be visualized. This technique enables us to understand more biological features of this cryptic termite.

Detection of Metabolic Gas Emitted by Termites Using Semiconductor Gas Sensors

ABSTRACT The feasibility of using three types of semiconductor gas sensors to detect the metabolic gas generated by termites was investigated. Odor, methane, and hydrogen sensors made of a tin oxid...