カイガラムシ類匍匐幼虫の風力による飛散実験

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  • Experiments on the dispersal of the crawling larvae of some Coccoidea (Homoptera) by air currents
  • カイガラムシルイ ホフク ヨウチュウ ノ フウリョク ニ ヨル ヒサン ジッケン

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It is well known that winds play an important part in the spread of Coccids. Especially interested readers may refer to Tutt (1898), Webster (1902), Quayle (1916), Dammerman (1922), Ehrlich (1933), Wolcott (1933), Clarke (1938), Glick (1939), Strickland (1950) and Bodenheimer (1951). But the literature reveals that not a single experiment has ever been carried out on the dispersal of Coccids by artificial air currents generated by an electric fan. The experiments reported herein on the dispersal of the crawling larvae of five species of Coccids by air currents were conducted in the Entomological Laboratory of Kyushu University at Fukuoka, Japan, from 1953 to 1954. In all experiments more than 1,500 crawling larvae of 0-24 hours age were used. The larvae were put on glass tubes of three different diameters (Tube A : 52.5 mm. Tube B : 22.0 mm. Tube C : 6.8 mm.). A wind tunnel was set betweenthe glass tube and the electric fan so as to make uniform currents to the tube.The larvae were oriented on eight imaginary positions on the surface of theglass tube to allow the fan to blow a current of air (Text-figure 1). The fan was regulated to deliver winds of desired velocities to the tube and allowed torun three minutes under room conditions, illumination being entirely natural. In the process of becoming familiar with the velocities of air currents which were sufficient enough to disperse the larvae, winds of various velocities were tested. The results were summarized in Tables 1-19, 20 and Text-figures 2-11. The percentage of the crawling larvae blown off by air currents was the highest on the sites III and IV?a remarkable contrast to the sites VI, VII and VIII. Judging by the flat structure of the larval body, the sites I and V seemed to be more stable for the larvae against air currents than the sites II, III and IV (Text-figures 9, 10 and 11). The experiments showed that many of the crawling larvae were blown off as insect drift within one minute after the beginning of each experiment as shown in Text-figure 8. The reaction of the larvae to winds was quite different according to the species of Coccids. All the crawling larvae (on sites I?V) of five species of Coccids used in this experiments reacted fairly well to much weaker air currents which correspond to No. 4 of Beaufort scale of wind velocity. The experiments suggested that the wind of the velocity No. 5 (fresh breeze) could carry almost all the crawling larvae (on sites I?V) from their crawling surface to the air as insect drift. The dispersal of the larvae of Ceroplastes rubens required much stronger air currents than those required by four other species. It is highly interesting that the crawling larvae of Icerya purchasi were very sensitive to the slightest movements of air and responded even to such wind as No. 0 of Beaufort scale of wind velocity. The sensitiveness of the crawling larvae among five species of Coccids was arranged in the following order from strong to weak : Icerya purchasi, Pulvinaria aurantii, Eriocerus pela, Phenacoccus aceris and Ceroplastes rubens.

カイガラムシ類の匍匐幼虫が, 風によつて分散させられることは,従来間接的な方法によつて調べられていた. 本研究では, それらの幼虫に, 実験的に直接に風を当て, 風力に対する反応を調べた. 実験に使つた5種類のカイガラムシの飼働幼虫は, 夫々Beaufortの風力階級4以下の弱い風に実によく反応し, ワタフキカイガラムシでは階級0の部分に属する気流の動きにも敏感に反応する個体が認められた.

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