M. Réaumur found upon trial, that it was not only the caterpillars hatched from the eggs of the same mother which would unite in constructing the common tent; for different broods, when put together, worked in the same social and harmonious manner. We ourselves ascertained, during the present summer (1829), that this principle of sociality is not confined to the same species, nor even to the same genus. The experiment which we tried was to confine two broods of different species to the same branch, by placing it in a glass of water to prevent their escape. The caterpillars which we experimented on were several broods of the brown-tail moth (_Porthesia auriflua_) and the lackey (_Clisiocampa neustria_). These we found to work with as much industry and harmony in constructing the common tent as if they had been at liberty on their native trees; and when the lackeys encountered the brown-tails they manifested no alarm nor uneasiness, but passed over the backs of one another, as if they had made only a portion of the branch. In none of their operations did they seem to be subject to any discipline, each individual appearing to work, in perfecting the structure, from individual instinct, in the same manner as was remarked by M. Huber in the case of the hive-bees. In making such experiments, it is obvious that the species of caterpillars experimented with must feed upon the same sort of plant.[BL] (J. R.) The design of the caterpillars in rolling up the leaves is not only to conceal themselves from birds and predatory insects, but also to protect themselves from the cuckoo-flies, which lie in wait in every quarter to deposit their eggs in their bodies, that their progeny may devour them. Their mode of concealment, however, though it appear to be cunningly contrived and skilfully executed, is not always successful, their enemies often discovering their hiding-place. We happened to see a remarkable instance of this last summer (1828), in the case of one of the lilac caterpillars which had changed into a chrysalis within the closely-folded leaf. A small ichneumon, aware it should seem of the very spot where the chrysalis lay within this leaf, was seen boring through it with her ovipositor, and introducing her eggs through the punctures thus made into the body of the dormant insect. We allowed her to lay all her eggs, about six in number, and then put the leaf under an inverted glass. In a few days the eggs of the cuckoo-fly were hatched, the grubs devoured the lilac chrysalis, and finally changed into pupæ in a case of yellow silk, and into perfect insects like their parents. (J. R.) _CHAPTER IX._ INSECTS FORMING HABITATIONS OF DETACHED LEAVES.