All through the autumn and winter the gall-insects do nothing inside their houses. Indeed we can take them out and keep them in little vials, and most of them get on very well. They require no food; they simply want to be let alone. But in early spring--and spring in California comes very early; indeed, it comes in winter!--they wake up and in a short time change into stout-bodied little real insect-looking insects with six legs, four wings, a round head with feelers and eyes and whatever else an insect's head ought to have. Especially sharp jaws. For each gall-dweller has now to get out of its house. And as there are no doors, it has to make them. Which it does with its sharp jaws, gnawing a tunnel from the center of the house right out through the thick hard wall to the outside. When it gets out it flies around in lively manner for a few days, finally settling on a sprouting oak-leaf or bud or green stem or twig, and laying a few eggs, or several, or many, according to the habits of its special kind, and then it dies. And when the tiny white grubs hatch from these eggs, new houses begin to be made around them by the oak-trees, and a new generation of gall-insects is fairly started. But not all the dwellers in the houses of oak have such a smooth and easy life as I have described. There will often come out of one of the galls that Mary and I have in a tarlatan bag, not one kind of insect, but several kinds, and only one of these kinds is the regular proper house-owner. The others are interlopers. Some of them may be only uninvited but not especially harmful guests, just other kinds of gall-insects that seem to have given up the habit--if they ever had it--of starting houses of their own, and have adopted the cuckoo-like way of laying their eggs in the just-starting houses of other gall-insects. The grubs, or young of these messmate gall-insects, live in, and feed on, the same house, with the rightful dwellers, but as the oak-tree has plenty of sap and the gall-house is usually large enough for all, there is generally no harm done by these cuckoo intruders. But some of the intruding insects that come from our galls are not so harmless. They are the ones called parasites. They live in the houses not for the sake of the protection or the food furnished by the house, but in order to eat the actual dwellers in the house. Often and often not a single real gall-insect would come out in the spring from many of our collected houses, but only a little swarm, or sometimes just two or three or even one, of these insect-devouring parasites that has eaten up the rightful owners of the houses.