Morphological comparison of proboscides and associated sensilla of Helicoverpa armigera and Mythimna separate (Lepidoptera: Noctuidae)

Abstract

Proboscides are important feeding devices for most adult Lepidoptera and exhibit significant morphological modifications and types of sensilla associated with feeding habits. In this study the architectures of the proboscides and sensilla were compared between the cotton bollworm Helicoverpa armigera (Hübner) and the armyworm Mythimna separate (Walker) using scanning electron microscopy. The proboscides of both species consist of two elongated maxillary galeae joined by dorsal and ventral legulae, forming a food canal. The dorsal legulae in H. armigera disappear a short distance from the proboscis apex, whereas those in M. separate exist up to the apex. Three types of sensilla are present on the proboscides of both species: sensilla chaetica, basiconica, and styloconica. The morphological differences of the sensilla mainly concern the sensilla styloconica, whose styli have six to seven smooth-edged ridges in H. armigera but six serrate-edged ridges in M. separate. No significant sexual dimorphism was found in the proboscides and sensilla of both species except for the length of the zone without the dorsal legulae in H. armigera. The morphological similarities and differences of the proboscides and sensilla between the two species are briefly discussed.