Morphology of the immature stages of Agrotis canities and A. robusta and an identification key of Agrotis species associated to economic crops in South America

Abstract

Agrotis Ochsenheimer (Lepidoptera: Noctuidae) is a widespread, cosmopolitan genus, with 20 species occurring in South America. Two of those species are considered major pests of different crops, Agrotis ipsilon (Hufnagel) and Agrotis robusta (Blanchard). The latter is often confused with Agrotis malefida Guenée in the literature and, despite its economic importance, its immature stages have been only superficially described. Agrotis canities (Grote), although never regarded as a pest, is known to use some crops as hosts and is commonly captured in light traps. However, its immature stages are unknown, making the evaluation of its true economic importance difficult. In this study, we examine in detail the external morphology and ultrastructure of the egg, larva and pupa of A. robusta and A. canities using light and scanning electron microscopy. Furthermore, we provide an identification key for those four species including all immature stages and up-to-date maps of their distribution in South America. Finally, we discussed the application of immature stages morphology of Agrotis species in systematic and phylogenetic studies. Particularly, we examine the morphology of the trichobothria, or “tonosensillum”, through larval development and the progressive and differential development of abdominal legs in each species.