Butterfly guru Nigel Venters has provided this excellent illustration which shows clearly how to tell the sex of Monarch butterfly pupae.

This is just one of the subjects to be covered at The Commercial Butterfly Breeders Seminar, which will be held in Orlando, Florida, on Friday November 2nd 2001. Other seminar topics will include “target” egg laying for several species: controlling the location of egg laying; and “tub-less” larvae, start to finish so that larvae are never subjected to closed boxes, reduced airflow, increased humidity and disease-causing dampness!

http://www.butterflybreeders.org/graphics/Monarchpupasex11.jpg