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生存在地球上的昆虫约有100万种,而为害农作物的昆虫约有1万多种。昆虫的分布很广,大部分和人类有密切的关系。其中有不少是益虫,如家蚕、蜜蜂、白腊虫等,还有寄生或捕食害虫的寄生蜂和肉食性昆虫。因此,在植物保护工作中必须分清益虫和害虫,大力消灭害虫,保护和利用益虫。一、昆虫的一生变化在昆虫个体发育过程中,从卵孵出幼虫叫孵化。初孵化出来的幼虫叫做第一龄幼虫,经过第一次脱皮后叫第二龄幼虫,以后每脱皮一次就增加一龄。两次脱皮相隔的时间,叫做龄期,末龄幼虫停止取食不再生长,就叫老熟幼
There are about 1 million insects that live on Earth, and about 10,000 species of insects that damage crops. Insects are widely distributed, most of them are closely related to humans. Many of them are beneficial insects such as silkworms, bees, waxworms and the like, as well as parasitic and carnivorous insects that parasitize or prey on pests. Therefore, we must distinguish between beneficial insects and pests in plant protection work, vigorously eliminate pests and protect and utilize beneficial insects. First, the insect’s life changes In the development of individual insects, hatching from eggs hatch larvae. The newly hatched larvae are called the first instar larvae. After the first larvae are called the second instar larvae, the first instar larvae are increased by one each time they are peeled off. Two times peeling off time, called the age, the last instar larvae stop feeding no longer grow, called the old cooked young