No. 64] DIPTERA OF CONNECTICUT: MORrilULOGY 85 



the segments precedino- them, but as we pass to the BrachA'cera whose 

 lines of descent approach those of the Cyclorrhapha, we frequently 

 encounter instances of a modification of the eighth segment (Fig. 12, 

 A) as well as the seventh segment (Fig. 12, C) and even the sixth 

 segment (Fig. 10, D), to form a rather imperfectly differentiated 

 postabdomen, which may even undergo a "preliminary" distortion 

 (Fig. 12, B) foreshadowing the modifications Avhich reach their final 

 culmination in the distorted postabdomen of male Cyclorrhapha. 



The Parts of the Male Genital Segment. The ninth segment of 

 the male exhibits the greatest variability, and its structures are con- 

 secjuently of great taxonomic value in most male Diptera. The 

 problem of determining the homologies of the male genitalia, how- 

 ever, is an extremely difficult one (as is the case with the male geni- 

 talia of insects in general), and much work remains to be clone before 

 a uniform terminology can be successfully applied to the genitalic 

 structures in all male Diptera. 



Despite the contentions of other investigators to the contrary, the 

 writer would vigorously insist that if comparative morphology has any 

 meaning at all, the segmented genital f<)rcej)s flanking the aedeaigus 

 in male Mecoptera, Trichoptera, Diptera, etc., nmst be homologous 

 with the genital forceps, or parameres, tlanking the aedeagus in male 

 Hymenoptera, Coleoptera, etc.. instead of representing the coxites 

 and styli of lower insects, as is maintained by other investigators. 

 The ontogenetic development of the parts, so far as they liave been 

 studied, may readily be interpreted as supporting this view, and it 

 is very difficult to understand why the segmented genital forceps of 

 male Diptera. Mecoptera, etc., which are strikingly similar to those 

 of the closely related Hymenoptera, are not interpreted alike in these 

 closelj' related Holometabola ! 



Ontogenetically, the aedeagus and parameres develop from paired 

 lobes borne on the ninth sternite in the immature stages of male 

 Holometabola. and these lobes become differentiated into the structures 

 forming the median aedeagus, with its flanking parameres borne on a 

 basal ring, in the adult. The flanking parameres, borne on a very 

 broad basal ring, are unsegmented in such primitive Holometabola 

 as the lampyrid beetle Lucidota corrusca, while in the primitive hy- 

 menopteron Xycla. the basal ring becomes greatly reduced in size, 

 and the formerh^ unsegmented parameres now become two-segmented 

 genital forceps flanking the median aedeagus formed by the union 

 of the paired penis valves, or aedeagal valves, which unite to form 

 the sclerotized tube through which the ejaculatory duct opens to the 

 exterior (frequently by means of a membranous eversible penis). In 

 the Trichoptera. Mecoptera, Diptera, etc., the basal ring is usually 

 obliterated, and the parameres. which are usually two-segmented in 

 the primitive representatives of these orders, form the genital forceps 

 flanking the median aedeagus, as was pointed out by the writer in 

 Vol. 28, page 8. of the Bulletin of the Brooklyn Entomological So- 

 ciety for 1938.* The basal segments of the genital forceps will be 



* See also the recent discussion of these structures in male Diptera in the September 

 issue of "Psyche" for 1941. 



