Rice leafminer - rice leafminer

This insect belongs to the family Agromyzidae, suborder Brachyceratopsid, group of flies, order Diptera, suborder Brachyceratopsid. It is distributed throughout Japan, and its larvae are pests that parasitize rice and cause damage. The adult is 2.8 mm long and 3.2 mm long. Its body is black and its forehead is wide, wider than the width of one compound eye. Its antennae are short and have fine hairs on their setae. Its wings are transparent and have no markings. The egg-laying season is when the seedlings in the nursery open their second leaves, and eggs are laid one by one in the leaf flesh near the tip of the leaf. The egg-laying scars are white, elongated, and appear in discontinuities. If you look carefully through the scarred leaf, you can find oval eggs about 0.5 mm in size. The egg stage lasts for 5 to 6 days, and the hatched larvae feed in a bag-like shape while burrowing into the leaf flesh. The larval stage lasts for 10-14 days, and the fully grown larvae (maggots) reach a body length of 5-6 mm. Infested leaves turn white from the tips and wither. Pupae are often found on the leaf surface, and two types are known to exist. The thin, brown-bodied ones are non-dormant and emerge after 10 days in the pupal stage. The short, thick, black-bodied ones hibernate and overwinter. Two generations occur per year. This species is originally a northern insect, and damage to rice crops is relatively common in Hokkaido, the Tohoku region, and the Hokuriku region.

[Shushiro Ito]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

昆虫綱双翅(そうし)目短角亜目ハエ群ハモグリバエ科に属する昆虫。日本各地に分布し、幼虫はイネに寄生して被害を与える害虫。成虫の体長は2.8ミリメートル、翅長3.2ミリメートルで、体は黒色で頭部前額(ぜんがく)は幅広く、1複眼の幅よりも広い。触角は短小で、触角の刺毛には微毛がある。はねは透明で斑紋(はんもん)はない。産卵期は苗代の苗が双葉を開くころで、卵は葉先近くの葉肉内に1個ずつ産み付けられる。産卵傷は白色で細長く、とぎれて現れる。傷葉(きずば)を注意深く透かしてみると、楕円(だえん)形の0.5ミリメートルぐらいの卵がみつかる。卵期は5～6日で、孵化(ふか)した幼虫は葉肉内を潜行しつつ袋状に食害する。幼虫期は10～14日で、成長した幼虫（ウジ）は体長5～6ミリメートルとなる。被害葉は葉先から白く変色して枯れる。蛹(さなぎ)は葉面でみつかるものが多いが、これには2型あることが知られている。体が細くて褐色を帯びたものは不休眠で、蛹(よう)期は10日で羽化する。体が太短くて黒色を帯びたものは休眠して越冬する。1年に2世代発生する。本種は、元来北方系の昆虫であり、稲作の被害は北海道、東北地方、北陸地方に比較的多い。

［伊藤修四郎］

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