If you find a spider at night, kill it even though it were your mother or father.
If you find spiders at night, kill them even though they were your parents.
"夜の蜘蛛は親でも殺せ"
夜蜘蛛は縁起が悪い生き物という言い伝えから「夜の蜘蛛は親でも殺せ」といいますね。
直訳してみました。
蜘蛛 a spider, spiders
夜に at night
見つける find
殺す kill
たとえ～でも even though, even if
If you find a spider at night, kill it even though it were your mother or father.
If you find spiders at night, kill them even though they were your parents.
日本 
