Last modified: Aug. 11, 2020, 8:30 a.m.
This family, of cosmopolitan distribution, comprises about 1,450 described species. Most of these occur in the tropics, but many are found in the Holarctic region (van Nieukerken E. J., Kaila L., Kitching I. J., Kristensen N. P. (...) Yakovlev R. V., Zolotuhin V. V. & Zwick A. 2011: 216).
In the Western Palaearctic region, all species are day active. The caterpillars are off-white and live inside their host plants: they are endophagous. The abdominal legs (prolegs) carry two wreaths of hooks, making them easily distinguishable from beetle larvae.
It is often thought that Sesiidae caterpillars are xylophagous (feeding on wood) but they feed only on plant juices. For this reason, some species induce the formation of sap-rich galls on the host plant but many species also use existing galls or swellings on the host plant to develop.
In almost all cases also the pupation takes place inside the plant. On hatching, the pupa pushes itself halfway out of the plant before the imago emerges. Depending on the species, the future exit hole is more or less invisible or even not visible at all.