Cocoon silk chemistry of non-cyclostome Braconidae, with remarks on phylogenetic relationships within the Microgastrinae ( Hymenoptera:Braconidae)

Abstract

• Bulk amino acid composition was determined for cocoon silks for 54 species of non-cyclostome braconid wasps collectively representing 14 subfamilies. Little intraspecific variation was encountered either between conspecific individuals of differing origin or between physically different silk layers within a single cocoon. Variation within subfamilies was small except in the Microgastrinae. Most taxa, excluding most microgastrines, had silk of a fairly typical fibroin type with high relative abundances of alanine, serine or glycine (of which either alanine or serine was the most abundant) and usually with moderately low molar concentrations of presumed acidic residues (aspartate/asparagine (As(x)) and glutamate/glutamine (Gl(x))) which ranged from approximately 2% up to nearly 30% (in Helconinae and Blacinae). In the Microgastrinae, members of the genus Microplitis (four species) were similar to the other non-cyclostome subfamilies in having 14.3-26.1 molar % As(x), but the other 10 microgastrine genera investigated produced silks with As(x) the most abundant detected residue comprising 32.4-50.5 molar % while glycine represented less than 10% of residues, indicating an -helical silk. These data are discussed in the light of some recent independent phylogenetic studies on the Microgastrinae that also suggest a basal position for Microplitis within the subfamily, despite its apparently highly specialized biology.