1622. All insects are divided into two primary groups, which are either winged or apterous (not winged). 1. Winged insects (Ptilota Aristotle) undergo the changes we have already described; they are first larvï¾µ, then pupï¾µ, and finally become provided with four or two wings capable of flight. These are called perfect insects, and comprise all butterflies, bees, wasps, beetles, dragon-flies, flies, &c. Ants, likewise, enter into this great division; for although the majority of those which we see are without wings, still they are only the neuters or imperfect ants, the true males and females being each furnished with four wings. 2. Apterous insects, on the other hand, are those which in no period of their existence are ever furnished with wings; as the spider, centipede, crab, louse, &c. They undergo little or no metamorphosis; that is, they come from the egg nearly in the same form which they are destined always to preserve.