Characters for determining the sex of cutworms and other noctuid larvae (Lepidoptera: Noctuidae)

Abstract

External structures were found which permitted the accurate determination of males, or females, or both in the larvae of each of 40 species of noctuids.In males, the developing genitalia arise from a pyriform histoblast attached to the ventral cuticle near the anterior margin of the ninth abdominal segment. The cuticle is invaginated into this structure, which is visible externally as a slit, or as a depression, but it is often obscure. In some species the invaginated cuticle is strongly melanized, and consequently very distinct, but in most it is either colorless or too variable to be useful as the definitive sexual character.In females there is one pair of ovoid histoblasts attached to the ventral cuticle in each of the eighth and the ninth abdominal segments. Externally, the cuticle corresponding to these areas of attachment is modified; usually the cuticular sculpturing is reduced or absent, about, and sometimes beyond, these areas. Each area is usually recessed and forms a more or less distinct pit. These structures proved reliable for sexing larvae and in every species were located between the ventral and subventral setae in the eighth and ninth abdominal segments.