Usubakagero - Usubakagero

Japanese: ウスバカゲロウ - うすばかげろう

A general term for insects in the Myrna family of the Insecta order, and one of its species. This genus resembles dragonflies at first glance, but is more distantly related. It has a smaller head and thicker antennae than dragonflies. Its wings are also broader and softer than those of dragonflies, and it flies weakly and flutteringly, not as agile as dragonflies. Although it is called a mayfly, it is distantly related to mayflies in taxonomic terms and has a different morphology. It is found in Japan, as well as the Korean Peninsula, China, and Taiwan.

[Yamazaki Egane]

form

Hagenomyia micans , known in Japanese as Usubaka Mayfly, has a body length of 35 mm, with a forewing of around 40 mm. The body is thin and rod-shaped. The depression at the back of the head, the mouthparts, the ventral surface of the thorax, and the legs (excluding the black tarsus) are yellow. The wings are transparent with net-like veins, and there is a white spot a little before the tip of the leading edge. The larvae are called arijigoku (antlion), and have large jaws on their heads and short, bag-like bulging abdomens.

[Yamazaki Egane]

Ecology

Adults appear from June to October, and are often found in forests close to human settlements. They fly from dusk to night to prey on small insects such as mosquitoes, and also come to lights. Eggs are laid in the sandy soil under trees or eaves, and the larvae dig cone-shaped holes in the dry ground in the shade and hide in the sand at the bottom. When small insects such as ants slip down trying to pass through the hole, they flick the sand with their heads, causing them to drop to the bottom, then they clamp down with their large jaws and suck out the body fluids. The larvae mature in one to two years, spit silk in the soil, and create spherical cocoons about one centimeter in diameter wrapped in soil in which they pupate, soon emerging as adults and flying out into the forest.

[Yamazaki Egane]

Similar species

There are over 600 known species of Myrmeleonidae insects in the world, with 17 species found in Japan. Only a few, such as the small Myrmeleon formicarius and the starry Glenuroides japonicus, make mortar-shaped holes like those of antlions, while the giant Heoclisis japonica and the brown Distoleon nigricans live in the sand but do not make holes, and the spotted Dendroleon pupilaris lives on the ground's surface. Some species stick to depressions in the surface of rocks and prey on other insects.

[Yamazaki Egane]

Mayfly
It is found throughout Japan, and is often found in forests close to human settlements. Its body is thin and rod-like, and its transparent wings have net-like veins, with a white spot just before the tip of the leading edge. Wing span is about 85 mm. Family: Mayfly ©Shogakukan Photo by Okuyama Hisashi ">

Mayfly

Antlion
The larvae of the mayfly dig a funnel-shaped hole in the ground and hide there, catching small insects that slip into the hole. ©Shogakukan Photo by Hideyuki Asakura ">

Antlion

Antlion's Nest
The larvae of the mayfly, hiding in the bottom of a mortar-shaped hole, flick sand and soil onto any ants that have slipped into the hole, causing them to drop to the bottom, then pinch them with their large jaws and suck out their body fluids. The insects whose body fluids have been sucked out are then thrown out of the hole. ©Shogakukan Photo by Okuyama Hisashi ">

Antlion's Nest

Mayfly cocoon
Mature larvae spin silk in the soil and create a spherical cocoon about 1 cm in diameter wrapped in soil. The photo shows one that has been dug up from the soil. ©Shogakukan Photo by Okuyama Hisashi ">

Mayfly cocoon

Mayfly pupa
The silkworm pupates inside the cocoon, and soon emerges as an adult and flies off into the forest. The photo shows a partially opened cocoon. ©Shogakukan Photo by Okuyama Hisashi ">

Mayfly pupa

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

昆虫綱脈翅(みゃくし)目ウスバカゲロウ科の昆虫の総称、およびその1種。この類は、一見トンボに似ているが類縁は遠い。トンボより頭部が小さく、触角も太い。はねもトンボより幅広くて柔らかく、飛び方もひらひらと弱々しく、トンボのように敏捷(びんしょう)でない。また、カゲロウの名をもつが、カゲロウ類とも分類学上遠縁で、形態も異なっている。日本のほか、朝鮮半島、中国、台湾に分布する。

［山崎柄根］

形態

和名ウスバカゲロウHagenomyia micansは、体長35ミリメートルで、前ばねは40ミリメートル内外。体は細くて棒状。後頭のくぼみや口器、胸部腹面、黒色の跗節(ふせつ)を除く肢(し)部などは黄色。はねは透明で網状の脈があり、前縁の先端からすこし手前に白点がある。幼虫はアリジゴク（蟻地獄）とよばれ、頭部に大きなあごをもち、腹部は短く、袋状に膨らんでいる。

［山崎柄根］

生態

成虫は6～10月に現れ、人家に近い林に多い。夕方から夜にかけ、カなどの小虫を捕食するために飛び、灯火にもやってくる。卵は樹下や軒下などの砂土に産み付けられ、幼虫は日陰の乾いた地表にすり鉢形の穴を掘り、底の砂土中に潜んでいる。穴を通過しようとしてずり落ちたアリなどの小昆虫に、頭で砂土をはじきかけて底へ落とし、大きなあごで挟んで体液を吸う。幼虫は1～2年で成熟し、土中で糸を吐き、土に包まれた直径1センチメートルほどの球形の繭をつくって蛹(さなぎ)になり、まもなく成虫となって樹林へと飛び立つ。

［山崎柄根］

近似種

ウスバカゲロウ科Myrmeleonidaeの昆虫は、世界に600種以上が知られ、日本には17種を産する。アリジゴクのすり鉢形の穴をつくるものは、コウスバカゲロウMyrmeleon formicarius、ホシウスバカゲロウGlenuroides japonicusなど一部のものに限られ、オオウスバカゲロウHeoclisis japonica、カスリウスバカゲロウDistoleon nigricansなどは砂中にすむが穴をつくらず、マダラウスバカゲロウDendroleon pupilarisなどは地表にいる。岩石の表面のくぼみに張り付いて、ほかの昆虫を捕食するものもある。

［山崎柄根］

ウスバカゲロウ

アリジゴク

アリジゴクの巣

ウスバカゲロウの繭

ウスバカゲロウの蛹

出典　小学館　日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について　情報 | 凡例

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