Morphometric Description of the Final Instar Nymphs and Exuviae of Odonata: Tramea limbata Des.

Abstract

Tramea limbata, commonly known as the Black marsh trotter, is a dragonfly species belonging to the genus Tramea in the family Libellulidae. It has a cosmopolitan distribution found in various regions, including the peninsular region of India. This medium-sized red hued dragonfly is characterised by its distinctively long anal appendages. One key distinguishing feature of Tramea limbata is the presence of a dark-brown hind-wing patch. Both males and females exhibit red colouration, although females may also have a yellowish hue. The nymphs of Tramea limbata are robust, greenish-yellow and translucent aquatic insects. The study describes the morphology and morphometric characteristics of the nymphs and their exuviae (shed exoskeletons). The significant identifying characteristics noted are premental setae on the underside of the head and the lack of spiniform setae in the dorsal regions of the abdominal segments, particularly segments 6 to 9, giving them a smooth appearance. Notably, the appendages exhibit distinct patterns. The femur bears spines, while the tibia and tarsus are adorned with comb-like tufts of setae. These features help to distinguish Tramea limbata nymphs from strikingly similar nymphs of other Tramea species.