37G 



ME. WALTER WESCHE ON THE GENITALIA OF 



Table of Eelationship of Genitalia and Mouth-armature in Diptera. 



I liave often sought for the I'eason why the armature of the male mouth is less than 

 that of the females in the blood-suckinar CulicidsB and Tahauid*. 



Compensatiom of development of Tropin and Genitalia. — The idea of an identical law 

 of growth affords some explanation, because if that law exists it would include com- 

 pensation ; that is to say, if the mouth-parts were much developed, the genitalia might 

 be expected to be simpler or vice versa. Let us apply this test, and see how it 

 works out. 



Differences in mouth of males and females. — The armature of the female Tabanid 

 mouth consists of mandibles, maxillae (the stipites, cardines, and galeae), the maxillary 

 palpi (the labial are aborted), the hypopharynx and the part usually called the labruiu 

 (the fusion of the laciniae of the maxillae), and the labium bearing the usual tracheated 

 paraglossae (labella). 



The males have no mandibles, and the maxillae are rudimentary or atrophying, but 

 have the other parts that the female possesses. 



1. Now as regards the genitalia, the females have a very simple type of ovipositor, 



