A simple method for sexing live larvae of pink bollworm, Pectinophora gossypiella (Lepidoptera: Gelechiidae)

Abstract

Abstract Lepidopteran adults can be sexed using different morphological characters because sexual dimorphism is prevalent in most species. But sometimes, necessity arises for the sexual differentiation of immature stages like larvae so that virgin females can be studied. Here, we present a straightforward, reliable, and non-invasive method that permits sexing of Pectinophora gossypiella (Saunders, 1844) (Lepidoptera: Gelechiidae) larvae during their fourth instar. Male P. gossypiella larvae are identified by their testes, which are visible through the dorsal integument of the abdominal segments. The testes are observed as two dark elliptical bodies, one on either side of the midline of the fifth abdominal segment in the fourth instar of P. gossypiella . Length and width of the individual testes was measured as 653.33 ± 5.68 and 484.89 ± 4.34 μ m, respectively, in P. gossypiella . After separation of live male larvae by these characters, they were transferred into separate vials and emerged adults were identified to ascertain correct identification of the males. We observed that all the larvae with dark-coloured testes visible to the naked eye in their fifth abdominal segment during the fourth instar developed into male moths and all other larvae without this character developed into female moths. The visual sexing of male and female larvae of P. gossypiella could save time in separating the sexes to carry out studies on sex-specific responses, hybrid mating, and/or inheritance of insecticide resistance.