Sexing larva by pits on belly

I found this info in a Lepidopterists Society Journal 1994 Volume 48 Number 3 if you want to read the full article. This method was tested on fith instar larva of Eucheira socialis, Battus philenor, Junonia coenia and Papilio zelicaon. Do not know if this works on moths or other butterfly species. The 9th segment on a male larva has one pit. There are two pits each on the 8th and 9th segment on a female larva. Look on the belly of the larva to find the pits. Use hand lense or scope with 20x magnification to see pits. It was hard to sex P. zelicaon because the pits were pale with no contrasting color. The J. coenia larva could be sexed as early as the third instar. In the female of E. socialis females were esyest to sex between second and forth instar while at the same stages it was almost imposible to sex males. The male E. socials were easyest to sex during fith and sixth instars when the pit was darkened.

If this is found to work on many other species it will be very helpful for those folks who send only male pupa to butterfly exibits around the world.