EXTERNAL SEX BRAND MORPHOLOGY OF 
THREE SULPHUR BUTTERFLIES 
(LEPIDOPTERA: PIERID AE)* 
By Richard S. Vetter 
and 
Ronald L. Rutowski 
Department of Zoology 
Arizona State University 
Tempe, Arizona 85281 
Introduction 
Males of many pierid butterflies have specialized scales, in 
patches or scattered over the wing surface, that are thought to be 
involved in the dissemination of a chemical signal (Chapman, 1971). 
Recent experiments with two sulphurs, Eurema lisa Boisduval and 
Leconte and Colias philodice Latreille, have borne out this assump- 
tion (Rutowski 1977, 1979). In these species, the male has a patch of 
cells and scales in the friction area of either the ventral forewing {E. 
lisa) or the dorsal hind wing (C. philodice ) that produces a chemical 
signal used to seduce females during successful courtship. Females 
respond to the chemical signal by extending the abdomen ventrally 
out from between the hindwings, thereby permitting copulation. 
In many sulphur butterflies the males’ sex brands are much more 
distinctive than those found in E. lisa and C. philodice. It is the 
purpose of this report to document the external morphology of the 
male sex brands of three species of pierids, Nathalis iole Boisduval, 
Eurema nicippe Cramer, and Colias cesonia Stoll, (Figure 1A). 
These species were chosen for two reasons: 1) they appear to 
represent a range of sex brand morphologies typical of that found in 
the pierid tribe, Coliadini (sulphurs), and 2) they have close 
affinities to species for which the function of the sex brand is well- 
documented. A special effort will be made to understand the 
possible adaptive significance of this variation in sex brand 
structure. 
* Manuscript received by the editor February 16, 1979. 
383 
