Social Caterpillars - Shelter Building

Shelter Building

The preeminent silk-spinners are the lepidopterous caterpillars. Caterpillars spin silk prolifically and in comparison to other non-eusocial insects build large and relatively complex structures from the material. Moreover, they are the only insects outside of the Hymenoptera and Isoptera to exhibit true collective building behavior involving colony-wide synchronization of activity and periodic shelter expansion. Some social caterpillars such as Brassolis isthmia and Archips cervasivoranus employ silk to draw the leaves of their host plants into tightly bound shelters in which they rest between foraging bouts. But the most impressive structures collectively built by caterpillars, such as the remarkable bolsa of the social pierid Eucheira socialis and the tents of the lasiocampid caterpillars, are made exclusively of silk. The communal shelters of caterpillars are multifunctional, serving to facilitate basking and thermoregulation, molting, and antipredator defense. They may also serve as communication centers where hungry caterpillars are recruited to food finds. Little is known of the behavioral mechanisms that give rise to the architecturally distinct, collectively built shelters of caterpillars.

Unlike the complex, free-form structures of the eusocial insects, the ultimate shape that the nests of caterpillars take is determined to no small extent by exogenous factors. While colonies may actively select sites prior to the construction of a shelter, or abandon a site that proves inadequate after the shelter-building process has begun, all collectively built caterpillar shelters are formed either by pulling together plant parts or by spinning silk about a framework of branches and leaves. Studies suggest that subtle differences in the intrinsic properties of the silks of caterpillars, or the way they are spun, may be more important than overt differences in larval motor patterns in accounting for interspecific differences in the form of the web-nest.