Entomological Society of Chittagong University

Author:Nusrat Jannat Nisha

Orgyia sp., the Vapourer moth, is a common species of Lymantriinae (Erebidae).The adult males and females look drastically different and behave differently too; this is called sexual dimorphism. This is where it becomes very interesting!

The most fascinating aspect of this species is that the females are essentially wingless. “Wingless” isn’t quite the right term. The females do have wings, but they are reduced to tiny, non-functional stubs. This is similar to vestigial structures in other animals, like the leg bones in snakes, hipbones in whales, and tailbones in humans. This phenomenon is called brachypterism. Brachypterism takes the common sexual dimorphism seen in moths to an extreme level, turning the female into more of an egg-laying machine. This adaptation allows females to have a higher body mass, as being heavier no longer hinders their mobility, and they can save energy by not developing wings and flight muscles.
Females spend the rest of their short lives clinging to their cocoon. They begin to release a pheromone that will attract a male to them, to mate and ensure the next generation.

I’ve never seen a wingless moth before; glad I reared it .

Ref: Anonymous (2017) Life cycle of a vapourer moth. In: Naturalist Nightingale, Discovering the beauty of nature in the northwest. Available from: https://naturalistnightingale.wordpress.com/ (Accessed on:4 July,24 )