METAMORPHOSIS
to have some kind of protection, either from the weather, or from predacious creatures that might destroy it. While most pupae are protected in one way or another, there are mme that remain in exposed situations with no kind of shelter or concealment. The mosquito pupa is one of these, for it lires in the water along with the larva and floats just beneath the surface (Fig. 174 F), breathing by a pair of trumpetlike tubes that project above the surface from the anterior part of the body. The mos- quito pupa is a very active creature, and can propel itself through the water, usually downward, with almost as much agility as can the larva, and by this means probably avoids its enemies. The pupa of the common lady-beetle gives another example of an unprotected pupa (Fig. I32E). The larvae of these insects transform on the leaves where they have been feeding, and the pupae re- main here attached to the leaf, unable to move except by bending the body up and down. The pupae of mme of the butterflies also hang naked from the stems or leaves of plants. The pupae of many different kinds of insects are to be found in the ground, beneath stones, under the bark of trees, or ira tunnels of the leaves, twigs, or wood of plants where the larvae have spent their lives. Some of these, especially beetle pupae, are naked, soft-bodied creatures, depending on their concealment for protection. The pupae of moths and butterflies, however, are character- istically smooth, hard-shelled objects with the outlines of the legs and wings apparently sculptured on the sur- face (Plate ?4 F). Pupae of this kind are called chrysa- lides (singular, ch,7salis ). Their dense covering is formed of a gluelike substance, exuded from the skin, that dries and forms a hard coating over the entire outer surface, binding the antennae, legs, and wings close to the body. In addition, the pupae of many moths are inclosed in a silk cocoon spun by the caterpillar. The caterpillars, as we shall learn in the next chapter, are provided with
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INSECTS
