1941] 
Male Diptera 
79 
THE TERMINAL ABDOMINAL STRUCTURES OF 
' MALE DIPTERA 
By G. C. Crampton, Ph.D. 
Massachusetts State College, Amherst, Mass. 
The interpretation of the structures here described, was 
worked out a number of years ago, in preparing the chap- 
ter on the morphology of the Diptera for the forthcoming 
volumes of the Diptera of Connecticut; but the publication 
of this work has been indefinitely postponed due to lack of 
funds for its publication. Since the facts brought out in 
this study are rather “revolutionary” and indicate that the 
current interpretations of the terminal structures of male 
Diptera should be drastically revised, it has seemed advis- 
able to present these facts at this time instead of waiting 
any longer to publish them. 
Many male Diptera are able to twist their terminal ab- 
dominal segments about at least temporarily, in adaptation 
to the different positions assumed by the males during 
copulation, and a permanent displacement of the parts may 
occur as early as the pupal stage in the Cyclorrhapha ( Calli - 
phord ) , or just after emerging from the pupal stage, as in 
the Culicidse, certain Tipulidse, etc. 
Even such primitive Diptera as the Tanyderid Protoplasa 
fitchii may exhibit an inversion of the ninth abdominal seg- 
ment, as is indicated by all of the males of this species which 
I have examined (suggesting that the rotation may be per- 
manent, instead of a temporary adaptation during copula- 
tion), and a permanent inversion of the ninth segment 
(which is rotated about the long axis through 180 degrees) 
occurs in male Culicidse, certain Tipulidse, etc., among the 
Nematocera. Among the Brachycera, an inversion, or tor- 
sion, may occur in certain Asilidse and Dolichopodidse, as 
well as in the Bombyliidse and Certidse, while a similar ten- 
dency toward a torsion of the parts is exhibited by the 
