Phenotypic variations in a seed-eating beetle: Evolutionary significance of wing polymorphism in Callosobruchus maculatus (F.) (Coleoptera: Bruchidae **)

Abstract

Study of the possible involvement of environmental and genetic factors in determining the evolution of phenotypic varieties in the pulse beetle, Callosobruchus maculatus (F.) fed on chickpea (Cicer arietinum L.) seeds was made. Callosobruchus maculatus (F.) appears in two distinct forms, referred to, herein, as short-winged and long-winged forms. Short-winged individuals were smaller than those with long wings, differing in several basic traits, such as, width of head and thorax, length of elytron and hind wing, degeneration of flight muscles and strength and formation of trachéal tissue in the thorax and dorso-longitudinal indirect flight muscles. As compared to the long-winged females, the short-winged females began egg laying earlier, producing more eggs with deposition of 1 – 6 eggs (comparatively smaller) singly on one chickpea seed, and had faster larval development and earlier death. The evolutionary significance of phenotypic polymorphism in C. maculatus may be an ecological response developing some basic characteristics for making utmost use of the environment and preferred food source availability.