A Review of the Larvae of Xyelidae, with Notes on the Family Classification (Hymenoptera)

Abstract

Larvae have now been associated with all 5 Nearctic genera of the family Xyelidae: Xyela Dalman, Pleroneura Konow, Macroxyela Kirby, Megaxyea Ashmead, and Xyelecia Ross. A key to the genera is given and each genus is described. Descriptions are given for Macroxyela ferruginea (Say), Megaxyela langstoni Ross, M. aviingrata (Dyar), Xyelecia nearctica Ross, Pleroneura borealis Felt, and 2 undetermined species of Pleroneura . The larva of X. nearctica is described for the first time. The larvae of Pleroneura are described in detail for the first time. A classification of the Xyelidae is proposed, based on larval and adult characters and known habits. Two subfamilies, each with 2 tribes, are included. The Xyelinae is divided into the Xyelini, with 1 genus, Xyela , which feeds in the staminate cones of pines, and the Pleroneurini, with 1 genus, Pleroneura , which is a shoot borer in fir and pine. The Macroxyelinae is separated into the Macroxyelini, with 2 genera, Macroxyela and Megaxyela , which are external feeders on elm and hickory, and the Xyeleciini, with 1 genus, Xyelecia , which is probably a shoot borer in fir. The larval characters presented substantiate the dichotomous grouping into 2 subfamilies which was previously suggested by adult characters. Therefore, 2 evolutionary lines probably exist within this family. The tribes represent further evolutionary developments within the subfamilies, and are based on habits as well as on larval and adult characters.