THE LIFE HISTORIES, DISTRIBUTION, AND IMMATURE FORMS OF THE NORTH AMERICAN SAWFLIES OF THE GENUS CEPHALCIA (HYMENOPTERA: PAMPHILIIDAE)

Abstract

In North America the genus Cephalcia Panzer includes 10 species. The californica group, californica Middlekauff, frontalis (Westwood), fulviceps (Rohwer), and probably hopkinsi (Rohwer), has large species with gregarious larvae which build frass nests on Pinus . The provancheri group, distincta (MacGillivray), provancheri (Huard), semidea (Cresson), and probably nigra Middlekauff, has smaller species with solitary larvae that build silk-tube shelters on Picea , Abies , or Tsuga . Two species fit in neither group: fascipennis (Cresson), a large species with weakly gregarious larvae that build frass nests on Picea , and marginata Middlekauff, a small species quite unlike those of the californica group, with gregarious larvae that build frass nests on Pinus . Californica and hopkinsi are western species, provancheri and fascipennis are transcontinental, and the others are eastern. Keys are given for larvae and adults.The immature forms are described; the larva of fascipennis in detail. Females have one more instar than males.The eggs of all species are laid on needles of the host tree with a small knob-like part inserted into the host tissue. The larvae, which eat previous years' foliage, develop rapidly and drop to the ground when through feeding. Larvae do not construct cocoons but overwinter in a cell formed in the soil. Pupation and emergence may occur the next spring, or after two or more winters in the soil.Sex is determined by whether or not the egg is fertilized, thus parthenogenesis is facultative and arrhenotokous. An exception is semidea , having thelyotokous parthenogenesis and no known males.