Comparison of Hindwing Hamuli from Five Species of Cereal Aphids (Hemiptera: Aphididae)

Abstract

Wing-coupling apparatuses of five species of cereal aphids [western wheat aphid, Diuraphis tritici (Gillette); corn leaf aphid, Rhopalosiphum maidis (Fitch); bird cherry-oat aphid, Rhopalosiphum padi (L.); greenbug, Schizaphis graminum (Rondani); and the English grain aphid, Sitobion avenae (F.)] were examined under a scanning electron microscope. The scanning electron micrographs showed that the wing-coupling apparatuses of the five cereal aphid species were similar to the structure found in the Russian wheat aphid, Diuraphis noxia (Mordvilko). The wing-coupling apparatuses were composed of a forewing fold and a set of spiral-shaped (or twice-curved) hindwing hamuli. The hindwing hamuli were not fish hook-like (or once-curved) structures. Previous light-microscopy description of fish hook-like hamuli was the result of limited resolving power and field depth of light microscopy. The number of hamuli varied among and within the aphid species. An asymmetric number of the hamuli between the left and right hindwings were also found in all aphids. Rhopalosiphum padi and D. tritici had the least number of the hamuli, ranging from one to four, whereas S. avenae had the most hamuli, ranging from five to seven. Wing-coupling mechanisms and possible use of the hamuli as a taxonomic character are discussed.