The antennae of Lepidoptera appear to be the main organs of smell. Many moth species fly only at night, or have flightless females, and so use pheromones for sexual attraction. Usually it is the female which emits the pheromone. which the males smell with the antennae. So the antennae of male moths of many species has a more feathery appearance than that of the female.

male

female

Hesperilla idothea showing sex brands on the male forewings

The male and female butterflies of many species in HESPERIIDAE differ in that the males have a long mark near the middle of each forewing.

male

female

Anthela acuta showing larger female

The abdomen of the female has to carry eggs, so in many species the abdomen of the female is fatter, and the wings bigger than those of the male.

female

male

Teia anartoides showing flightless female and winged male

In the family PSYCHIDAE, and in some species in other families, the female is flightless and has no wings at all.

female

male

Papilio aegeus showing differing wing colouring of the sexes

In some species, the female has a different pattern and coloration on the wings from that of the male.

In some species, there is no obvious difference between the sexes, and one must resort to dissection of the tip of the abdomen to examine the genitalia under a microscope in order to work out the sex of a specimen.