Practical Techniques and Accuracy for Sexing the Potato Tuberworm,Phthorimaea operculella(Lepidoptera: Gelechiidae)

Abstract

Numerous life history studies of the potato tuberworm, Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae), a serious pest that affects potato production worldwide, have been done (Langford & Cory 1932; Mukherjee 1949; Bartolini 1951; Stanev & Kaitazov 1962; Ai-Ali et al. 1975; Foot 1979, Chauhan & Verma 1991; Rondon 2009). Mukherjee (1949), Bartolini (1951), and Chauhan & Verma (1991) studied dimorphism of this species. Sexual dimorphism does not become evident until yellowish testes become visible in the fourth instar; gradual change in eye pigmentation shows different pupal stages (yellow, early red, middle red, late red, and black eye pupa) (Chauhan & Verma 1991). Mukherjee (1949) found that male pupae have a round pit-like genitalia in the middle of the 9th segment, while females have a single aperture on the 8th segment. No one has provided a practical description of pupal differentiation. Our objectives were (1) to sex male and female P operculella pupae and adults by using external morphological characteristics; and (2) to determine the accuracy of sex ratios by comparing 2 different sexing methods.