Leaf-cut weevil

A general term for insects of the family Attelabidae in the order Coleoptera of the class Insecta. This species has the habit of rolling up leaves to lay eggs. It is closely related to the family Curculionidae and is broadly divided into the subfamily Attelabinae and the subfamily Attelabidae, with about 30 species of the former and about 60 species of the latter distributed in Japan. Attelabidae actively roll leaves when the leaves are newly green. Females fly onto young leaves and walk along the main veins and leaf edges to measure the size of the leaf, then make a cut at a certain distance from the tip. The cut leaf hangs limply and eventually wilts, but the female folds the leaf in two and rolls it up from the tip. After rolling it up two times, she makes a hole in it and lays her eggs. Using her mouth and legs skillfully, she completes a cylindrical "cradle". The larvae eat the leaves rolled up inside and grow, then pupate inside. The method of cutting the leaves and the infested plants are consistent depending on the species.

The Japanese name for the leaf-rolling weevil, Apoderus jeklii , cuts the leaves of oak and birch in a horizontal line. The Japanese name for the small black leaf-rolling weevil, A. erythrogaster , cuts the leaves of roses and other trees in a straight line from both edges toward the main vein, while the Japanese name for the Japanese snowbell, Cyclotracherus roelofsi , cuts the leaves of Japanese snowbell in a horizontal J shape, leaving one edge of the leaf intact. The Japanese name for the long-horned leaf-rolling weevil, Paroplapoderus pardalis , cuts the leaves of oak and chestnut trees in an L shape. Only females roll the leaves; males hardly cooperate, and fly away after mating. The Japanese name for the long-horned leaf-rolling weevil, Paratrachelophorus longicornis , and the Japanese name for the long-horned leaf-rolling weevil, Henicolabus lewisii , may cut off completed cradles depending on the weather, and tend to do so on dry days. There are right-handed and left-handed cradles, but this is mostly determined by the individual, so it seems that insects have preferences just like humans have right-handed and left-handed preferences. Immediately after hatching, the eggs are parasitized by a flying wasp, and the larvae are preyed upon by the larvae of a ground beetle. As the shape of the cradle resembles a letter written in a scroll, it was called the "little cuckoo's letter," which eventually became the name of the insect.

[Kei Morimoto]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

昆虫綱甲虫目オトシブミ科Attelabidaeの昆虫の総称。この類は木の葉を巻いて産卵する習性をもち、ゾウムシ科に近縁で、オトシブミ亜科とチョッキリゾウムシ亜科に大別され、前者は約30種、後者は約60種が日本に分布する。オトシブミ類は新緑のころ盛んに葉を巻く。若葉の上に飛来した雌は主葉脈や葉縁を歩きながら葉の大きさを測り、先から一定の距離のところに切り目を入れる。切られた葉はだらりとぶら下がり、やがてしおれてくるが、雌はこの葉を二つに折り畳んで先から巻き上げる。2回転ほど巻いたころ、これに穴をあけて卵を産み込む。口と脚(あし)を巧みに使いながら円筒状の「ゆりかご」を完成させる。幼虫は内部に巻かれた葉を食べて成長し、その中で蛹(さなぎ)になる。葉の切り方と加害植物は種類によって一定している。

　和名オトシブミ（ナミオトシブミ）Apoderus jekliiは、クヌギやカンバ類などの葉を横一直線に切る。ヒメクロオトシブミA. erythrogasterはバラなどの葉を主葉脈に向かって両縁から直線状に切り、エゴツルクビオトシブミCycnotracherus roelofsiはエゴノキの葉を横J字状に片側の葉縁を残して切る。ゴマダラオトシブミParoplapoderus pardalisはカシやナラの葉をL字状に切る。葉を巻くのは雌のみで、雄はほとんど協力せず、交尾を終わると飛び去る。ヒゲナガオトシブミParatrachelophorus longicornisやリュイスアシナガオトシブミHenicolabus lewisiiは天候によって完成したゆりかごを切り落とすことがあり、乾燥した日に切り落とす傾向がみられる。ゆりかごには右巻きと左巻きがあるが、これは個体によってだいたい決まっているので、人間の右利き左利きのような癖が虫にもあるらしい。卵には、生まれた直後にオトシブミヤドリコバチが寄生し、また幼虫はアトキリゴミムシの幼虫に捕食される。ゆりかごの形が巻紙の手紙に似ていることから「ホトトギスの落し文」などといわれ、それが転じて虫の名になった。

［森本　桂］

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