The functional morphology of species-specific male structures and lack of female coevolution in Lytta (Adicolytta) eucera (Chevrolat 1834) (Coleoptera Meloidae)

Abstract

Possible functions of several species-specific, sexually dimorphic male structures and of the male genitalia of Lytta eucera were deduced from observations of behaviour in the field and captivity, and were used to test theories of sexual selection. The male rubbed and tapped on the female’s antennae with sexually dimorphic segments of his antennae, and on her elytra with brushes of setae on his hind tarsi. He forcefully grasped the female’s prothorax and at least occasionally perforated the female’s prothoracic membranes with his modified middle tibiae, and her relatively uniform, membranous vaginal lining with his strong aedeagal teeth. His aedeagal teeth snagged her vaginal lining, and his gonostyli usually pressed against a featureless external female intersegmental membrane. None of these male structures was used as a weapon or in threat displays. No female structure fitted tightly in a “lock-and-key” manner with any of the male structures, nor was any female structure capable of selectively impeding their use, thus ruling out some hypotheses explaining their species-specificity in males. Female resistance to males, including occasional violent “tantrum” displays, was energetic, persistent, and highly effective; the functional significance of this resistance is unclear. If females distinguish the stimuli produced by species-specific traits of male genitalia, as supposed by some hypotheses, they likely use higher-level analyses in the central nervous system rather than the locations of the particular sense organs that are stimulated.