176 
THE POSTERIOR STIGMATA OF DIPTEROUS 
LARVAE AS A DIAGNOSTIC CHARACTER: 
WITH ESPECIAL REFERENCE TO THE LARVAE 
INCRIMINATED IN CASES OF MYIASIS. 
By MALCOLM EYAN MACGREGOR, B.A. (Cantab.), F.R.M.S., 
Carnegie Student in Medical Entomology. 
(From the Bussey Institution, Forest Hills, Boston, Mass.) 
(With Plates XIV—XVI and 3 Text-figures.) 
During investigations at the Bussey Institution on the role played 
by certain dipterous larvae in experimentally induced myiasis, with the 
object if possible of clearing a little of the doubt with which so much of 
the question is shrouded, the need of good diagnostic characters for 
these larvae was brought forcibly to my attention. 
This need is one that is felt both by entomologists and physicians, 
since, when cases of myiasis are met with, it is of the greatest importance 
that the species of fly concerned shall be readily determined without 
the need of rearing the larvae to the adult stage, at best a method that 
can but seldom be undertaken, owing to the fact that the material that 
one has to pronounce upon is often dead. Thus at the suggestion of 
Dr Wheeler and Mr Brues, a careful comparison of the morphological 
characters of the posterior stigmata was undertaken, and though this 
cannot claim to be in any way the first of such studies, since there are 
many good illustrations of the various forms of stigmata occurring in 
the different larvae, notably in Dr C. Gordon Hewitt’s book, The House¬ 
fly, and Mr Nathan Bank’s paper on The structure of certain dipterous 
larvae, with special reference to those in Human Foods, as well as in 
the works of other authors, including several old papers ; yet I think 
