铜色长角沼蝇的习性和生活史的初步观察(双翅目:沼蝇科)

A PRELIMINARY OBSERVATION ON THE BIONOMICS AND LIFE-HISTORY OF SNAIL-KILLING FLY SEPEDON AENESCENS WIED.(DIPTERA:SCIOMYZIDAE)

长角沼蝇属幼虫可捕食鸭血吸虫(毛毕吸虫属)的中间宿主椎实螺,鸭血吸虫的尾蚴也可导致人的稻田皮炎;另一方面,长角沼蝇属的卵又是稻螟赤眼蜂(稻田螟虫卵的天敌)天然的交替寄主,因此长角沼蝇对卫生和农业都是有益的.本文初步观察了华东地区一种常见的长角沼蝇——铜色长角沼蝇的成蝇形态特征、活动场所、出现季节、螺类宿主、幼虫食性和生活史.成虫寿命在春季为2个月,夏季为40-50天,一卵块通常含20-30个卵;幼虫以活椎实螺饲养,幼虫是否能攻击活的椎实螺,视幼虫期和宿主螺大小有关;自卵产下发育到羽化为成虫,平均温度在26℃时约需20天,在321℃时约为13天。

The larvae of Sepedon and their allies are well known to kill the snail Lymnaea, which is an intermediate host of the duck schistomiasis,and the cercaria of the latter also causes paddyfield dermatitis in man.On the Other hand,the egg of snail-killing fly is an im- portant alternate host of Trichogramma,the egg-parasite of paddy borer,in rice field.It is of fairly benefit to agriculture as well as to health. In 1965,some bionomics of the common species Sepedon aenescens Wied was briefly ob- served in Shanghai,Hangzhou and several areas in Fujian Province,China.In spring,the adults may be found on the weeds,water weeds,rapeseed plants in full blossom,especially on wheats near by creeks,streams or ponds.Just after wheat harvest,the population of these in- sects decreases.When the rice has been planted widespreadly in late summer,the flies frequent the rice field and rest on the lower part of rice stems,and then the fly density may be very high,where the host,small muddy snail Lymnaea parva,presents abundantly.While in marsh, shallow ponds and narrow grassy creeks,their host is Lymnaea swinhoei. The adult lasts 2 months in laboratory in spring,and 40 or 50 days in summer.An egg batch generally consists of 20 to 30 eggs.The larvae may be reared by living Lymnaea snails, but whether the larva can attack the living Lymnaea snail is related to the larval stage and the host size.One larva takes or kills a living snail per day on the average.From egglaying to adult emerging,it lasts about 20 days at mean temperature 26℃,and about 13 days at 32℃.A redescription of Sepedon aenescens Wied is given in detail.