Stridulation and Courtship Behaviour of Four Endemic Pill-Millipedes, Arthrosphaera spp. (Sphaerotheriida: Arthrosphaeridae) of the Western Ghats of India

Abstract

Mating behaviour of four species of pill-millipedes under genus Arthrosphaera Pocock (Arthrosphaera dalyi Pocock and Arthrosphaera disticta Pocock, Arthrosphaera fumosa Pocock and Arthrosphaera magna Attems) endemic to the Western Ghats of Southern India was analyzed in mesocosms. Stridulation is a classical communication signal in males as well as females for mate selection. Conglobation (or volvation) is a mechanism of defence to protect from disturbance or avoid predation. If male touches female or vice versa they conglobate. To avoid disparity among individuals of the same species, volvating pill-millipedes evolved stridulation behaviour for communication. The male broadcasts appropriate signal to female through stridulation to advertise its interest in mating. The females test the male’s fitness by conglobation and suitable male uncoils the partner through stridulation signals. Male with its pygidium successfully uncoils the female and attains suitable orientation for courtship. Male pairs with female ventro–ventro contact in opposite direction to deposit sperm into the vulva of female. The duration of mating varies from species to species and usually a lapse from 3 to 30 min. Vibration generated by stridulation is species-specific and its perception mechanism in pill-millipedes is yet to be clearly understood. Present study emphasized the structure of stridulatory organs, mechanism of stridulation and pattern of mating behaviour in four species of pill-millipedes.