Embryonic Stage of Diabrotica virgifera (Coleoptera: Chrysomelidae) at Diapause1

The western corn rootworm (WCR), Diabrotica virgifera LeConte overwinters in the egg stage in central United States. George and Ortman (1965) demonstrated that diapause occurs in the egg and the rate of development to eclosion is affected by low temperature. Many insects undergo egg diapause, and it is common that chilling is required to promote hatch (Andrewartha and Birch 1954). In contrast to this common feature, the specific embryonic stage at diapause is highly variable (Lees 1955). The present report describes the embryonic stage of the WCR at diapause and points out an apparent difference in development between diapausing and nondiapausing chrysomelid embryos.