Ecobiology of the Tamil Bushbrown Butterfly, Mycalesis subdita Moore (Lepidoptera: Rhopalocera: Nymphalidae: Satyrinae) from Visakhapatnam, East Coast of Southern India

Abstract

The Tamil Bushbrown butterfly, Mycalesis subdita Moore, exhibits seasonal occurrence at Visakhapatnam, South India, from July to March. It relies on Brachiaria distachya (Linn.) Stapf. For oviposition and as a larval host. The butterfly typically lays eggs singly, though occasionally two eggs are laid. The larvae undergo five instars, characterized by a light green color and a pair of head horns. The pupae are dark green with minute white spots. The developmental period from egg to adult emergence ranges from 28 to 37 days (average 32.40±3.53 days) under laboratory conditions, which include a temperature of 28±2 °C, 80±10% relative humidity, and a day length of 12-14 hours. Early life stages (eggs, larvae, pupae) are observed on B. distachya for 210 days, spanning July to January, resulting in four to five overlapping generations annually. There is a higher frequency of early life stages from September to December, aligning with the rainy and winter seasons. This suggests that M. subdita may require moist and shady conditions for year-round occurrence and reproduction, conditions that are not consistently present in the study habitat, hence its limited seasonal presence. The larvae demonstrate efficient consumption and utilization of the host leaves, as indicated by various nutritional indices: approximate digestibility (AD) of 97.25% - 72.12%, efficiency of conversion of ingested food to body substance (ECI) of 7.14% - 20.31%, and efficiency of conversion of digested food to body substance (ECD) of 7.34% - 28.16%.