Moulting pattern and mortality during the final emergence of the Coromandel Marsh Dart Damselfly Ceriagrion coromandelianum (Zygoptera: Coenagrionidae) in central India

Abstract

The final emergence of the Coromandel Marsh Dart Damselfly Ceriagrion coromandelianum was studied for 50 days (22 January–12 March, 2011) from the botanical garden of Hislop College, Nagpur, India, (a semi controlled site) where small underground cement tubs/tanks are used to grow macrophytes by the Botany department. In C. coromandelianum emergence is asynchronous, diurnal and occurs between 07.00h and 18.00h. Stage-I starts when the ultimate instar nymph of C. coromandelianum leaves the water body, searches for a suitable place and then begins to shudder its body to detach the trapped pharate from the nymphal exuvia. The pharate exerts pressure on the thoracic tergites to split the cuticle. Stage-II starts when the head and thorax of the pharate emerges out of the split exuvia. The pharate struggles to remove its trapped body from the nymphal exuvia. During Stage-III, the wings expand but are opaque; pigmentation of the body occurs simultaneously all over the body. Soon the whole body develops its species specific coloration while the expanding wings gain transparency, unfold and separate out and now the imago is ready for its maiden flight. Stages I, II, and III occupy 31.66%, 11.73%, and 56.60% of the total moulting period, respectively. A total of 243 emergences occurred during the observation period, 158 emergences occurred in tanks containing Pistia stratiotes, while 65 emergences in tubs containing Nymphaea nouchali indicating that C. coromandelianum prefers P. stratiotes over N. nouchali for oviposition. Twenty deaths were recorded during the present observation. Failure to moult (15%) and failure to emerge completely out of the exuvia (85%) were the two reasons for mortality.