寄生体，客虫：一种同栖生物体，尤指生活在另一昆虫巢穴中的昆虫。

Zoology A commensal organism, especially an insect that lives in the nest or burrow of another species.

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比如不能择枝而栖，甚至连在草丛安家也成奢望的飞禽，只能在鼠洞里屈就，而其宿费就是在寒冬时节必须衔枝而归，这种鸟鼠同穴的景象只有在世界屋脊才能随处可见。

For instance, the birds who have no tree branches, or even plants, in which to make a nest have to compromise and to take shelter in rat holes, for which they must find some branches in winter time.

youdao

比如不能择枝而栖，甚至连在草丛安家也成奢望的飞禽，只能在鼠洞里屈就，而其宿费就是在寒冬时节必须衔枝而归，这种鸟鼠同穴的景象只有在世界屋脊才能随处可见。

For instance, the birds who have no tree branches, or even plants, in which to make a nest have to compromise and to take shelter in rat holes, for which they must find some branches in winter time.

youdao