The instincts of insects, well developed for certain functions, often present aberrations more or less whimsical and remarkable. The caterpillars of some butterflies, before changing into chrysalids, envelop themselves in a wellwoven cocoon capable of protecting them from noxious influences. Protected by this covering, the caterpillar changes into a chrysalid, and later into a butterfly, which perforates the end of the cocoon in order to emerge. When any external agency destroys the cocoon, normal metamorphosis becomes impossible, and the larva dies before its maturity. Fabre[39] questioned whether the caterpillar during the time of the weaving of the cocoon was capable of repairing it if it was damaged. For this object he cut with a pair of scissors the end of a cocoon in the course of construction by the caterpillar of the beautiful peacock-butterfly. In spite of the hole thus produced, the caterpillar continued its ordinary work without suspicion that it would be of no avail. On this occasion “the caterpillar of the peacock-butterfly, notwithstanding the certain fate of the future butterfly, continued peaceably to spin, without in the least modifying the regular progress of its labour; when the time had arrived for the putting in of the last defensive stitches it placed them in the perilous breach, but neglected to mend the destroyed part of the barricade. It performed its vain task, ignoring what was indispensable for success.” Even amongst fossorial wasps, the instincts of which are so admirably developed, harmony is far from perfect. Fabre endeavoured to ascertain what effect was produced on these insects by taking away the egg laid in the burrow. He chose for this experiment the fossorial wasp _Pelopæus_ (Fig. 5), which preys on spiders. He took away the egg which had been deposited in a carefully-prepared burrow, and watched the subsequent manœuvres. “The _Pelopæus_ continued to store up spiders for the stolen egg; it gathered provisions that were not to be eaten; it redoubled its efforts to replenish a larder that I was constantly robbing with my forceps.” The insect neither discontinued its fruitless task nor appeared to be aware of its fruitlessness. Here, then, is an example of a foiled maternal instinct that gained no useful end. [Illustration: FIG. 5.—_Pelopæus_ (after Buffon). ]