イボタロウヒゲナガゾウムシに関する生態学的研究I．: その周年経過及び産卵について

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  • Biological study on Anthribus niveovariegatus Roelofs, a predator of the Chinese wax scale, Ericerus pela Chavannes(anthribidae, Colepptera). I : Its annual life-cycle and oviposition
  • イボタロウヒゲナガゾウムシに関する生態学的研究-1-
  • イボタロウヒゲナガゾウムシ ニ カンスル セイタイガクテキ ケンキュウ 1

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Our knowledge on the insect-feeding habit of the family Anthribidae is restricted to those of several species of the genera Brachytarsus and Anthribus, both of which have been reared from Lecaniine scales. In the present paper I gave the results of my studies on the biology of Anthribus niveovariegatus Roelofs which was reared from Ericerus pela Chavannes in Fukuoka, Kyushu, together with the life-cycle of the latter species. As is shown in the Figure 1, the present species has but one generation a year and spends the summer, autumn and winter seasons in the adult stage (Fig. 1). The overwintered adult beetle appears and visits the host scales mainly at the beginning of May for oviposition. After copulation the female deposits her eggs within the chamber of the scales. Oviposition takes place during May, and most of the eggs are deposited until the middle of May. As in the cases of many other parasites and predators already pointed out by Clausen (1940), the feeding of the female beetle at the hole made in the scale by either her mandibles or ovipositor is a closely associated habit with her oviposition. Namely, the female beetle breaks the hardened integument of the scale with her mandibles, feed at the droplet of liquid which comes from the hole. After such performance the beetle turns round herself, thrusts her ovipositor into the hole and through the thin ventral body wall and places her egg eithin the egg chamber of the scale (Fig. 2-B). Observation made in the field shows that among the hosts harbouring beetles eggs 72 per cent of the eggs are deposited by the method mentioned above, ehile 28 per cent are laid by such methods as shown in the Figure 2-A and ?C. The egg is usually found attaching to the body walll of the host at the point of penertration of the ovipositor. Laboratory observation on the oviposition (vide Tables 1 and 2) were divided into two classes, viz. each individual beetle of the first class experiments was provided with 4 host scales per day and that of the second ones with 10. The results are as follows. The beetle deposits usually one to three eggs per day. The total number of eggs deposited by a single female ranges from 10 to 36, and there is no significant difference in the total number of deposited eggs between the two experimental classes mentioned above. The female deposits usually one egg in a single host, but sometimes two or more eggs are laid in one host scale. Only a single individual of the beetle may develop even in the large host scale. Therefore, the number of effective eggs which may give rise to the adult beetles is more significant in the increase of the beetle’s population than the total number of eggs were laid was 15.2 per cent in the first class and 7.5 per cent in the second. From this experiment it may not be difficult to recognize the tendency that the more the host scales are given daily the fewer is the case in which more than two eggs of the beetle are deposited or the more the effective eggs are laid. As is shown in the Table 4(1-2), the number of eggs deposited by a single beetle in the field varies with the host density, and the fact that the frequency of hosts harbouring two or more eggs was lower in the field but higher in confinement may be regarded as having a close connection with the desiccating condition of the tissue of the host scales in the field. Eggs of the scale are necessary to the beetle larvae for their development to the adult stage. Three larval instars are observed. The larval period varies with the date of oviposition, and especially the duration of the third instar depends considerably upon the hatching state of the male scale eggs. Emergence of the adult beetles ranges from the beginning of June to that of the next month, having the peak from the 10th of June to the 22nd of the same month.

一般にヒゲナガゾウムシ類は朽木や菌類等の植物性食餌を取るのが普通であるが，本科Anthribidaeの中Brachytarsus属に属する一部の種は肉食性で介殻虫類の卵を捕食することが従来から知られていた．その後本属の種の一部はAnthtibus属に移される様になつたので，現在では介殻虫の卵捕食性は上記2属の一部の種に見られる事となつた．このような習性を有するヒゲナガゾウムシは本邦から2種，即ち本種 Anthribus niveoveriegatus Roelofs イボタロウヒゲナガゾウムシ及び A.kuwanai Yuasa タマカイガラヒゲナガゾウムシが知られているが，これ等は何れも従来Brachytarsus属に編入されていたものである（中根 1952）．イボタロウヒゲナガゾウムシは本邦の他，中華人民共和国にも分布し，その名の示すようにEricerus pela Chavannes イボタロウカタカイガラムシの卵を捕食するのが普通であるが，叉Kermes属のカイガラムシも攻撃の対象となし，湯浅（1931）はLecanium kunoensis Kuwana タマカタカイガラムシからも本種らしいものを得たと報告しているので寄主の範囲は相当広いもののようである．他方タマカイガラヒゲナガゾウムシは普通Kermesの類を寄主となし，その習性は本種に類似している点が多い．このような肉食性ヒゲナガゾウ類の生態に就ては，矢野（1915）が最初に本種イボタロウヒゲナガゾウムシの卵捕食性を認めて以来，Brachytarsus fasciatus Foerster に関するSilvestri（1919），B, nebulosus Foersterに関するPrell（1925），本種に関するClausen（1940）等の研究があり，特にClausenは従来知られていなかつたゾウムシの産卵法を明かにした．又，断片的な生体の観察としては湯浅（1931a, 1931b, 1932）及び石井（1932）のタマカイガラヒゲナガゾウムシに関する報告がある．これ等の研究を綜合すると，カイガラムシの卵を捕食するヒゲナガゾウムシ類の生態は何れもよく類似していて，その寄主と同じく年一世代を繰り返す事，短期間（1,2ヶ月）に発育を完了すること，成虫態で休眠し休眠期間が長い事（約10ヶ月）等の共通点を認めることが出来る．この最後の項に関しては従来の筆者は皆推測に止つていたのであるが，私は本種について之を確める事が出来た．本研究は1952及び1953の両年福岡に於て行つたもので，Ligustrum japonicum Thunberg ネズミモチに寄生するイボタロウカタカイガラムシを材料とし，そのBiological complex解明の一つの基礎として実施したものである．尚，本稿に於てはカイガラムシの生活史及び本種の周年経過，産卵に就て述べ，第二報には発育経過，休眠及びゾウムシの体調に及ぼす奇主の大きさの影響に就いて述べる．文献及び摘要は第二報にまとめて記した．

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