Differentiating Callosobruchus of South India with Special Reference to Callosobruchus maculatus - A Useful Guide for Entomologists and Non-Entomologists

Abstract

Losses of seed produce in pulses due to seed beetles is a very serious problem faced by farmers and traders during storage. Resistance (or susceptibility) and the degree of damage in legume seeds differ with respect to different bruchid species. The seed beetles, Callosobruchus chinensis and C. maculatus, are the two most widespread bruchid species in Southern India, which is being potentially misidentified. With this perspective, fundamental studies on their morphology are of great importance for correct identification, species specific resistant variety improvement and management. For a reliable and effective resistance evaluation in breeding program, a known, identified species or biotype must be employed. In this study, dissection of striking external morphological characters of both the species was done for comparisons. Type of antennae and hind femur are two common characters used for distinguishing these allied species. However, the most reliable genus and species indicators are variation in the spines on the underside of hind femur. The possible distinguishing characters of these two widespread species are illustrated in light of previously published literatures including other rare Callosobruchus species found in India viz. C. nigritus and C. orientalis, reported from Manipur, India. Furthermore, Scanning Electron Microscope study of South Indian C. maculatus strain revealed the presence of different types of sensilla on mouthparts and antennal regions, which had different functions. It is expected that this paper will provide practical information to both entomologists and non-entomologists working on bruchids especially plant breeders involved in resistant varietal development in the tropics and sub-tropical countries.