80 CON'NECTICX'T GEOL. AXD NAT. HIST. SURVEY [Bull. 



3. The terminal abdominal structures of female Diptera 



The, chief '"Landmark"" for identifying the segments in the pos- 

 terioi- region of the abdomen of female Di^^tera. is the "female gono- 

 l)ore*'. {fg of Fig. ^a) which is located (as it is in other insects) be- 

 tween the eio-hth and nintli sterna, or behind thei eighth sternite: and 

 the statement of Balfour-Browne (1932, p. 172), that "it is generally 

 agreed that the female gonopore in Diptera is situated behind the 

 9th sternam". is quite misleading. Furthermore, his view that tlie 

 Irue iirst abdominal segment has been absorbed in the metathorax. 

 and that each apjiarent segment should consequently receive a higher 

 numbei- is erroneous, as is also true of the view of Huckett (1924), 

 who considers that the occurrence of two pairs of spiracles in the 

 sixth segment of the postabdomen of muscoid flies (Fig. 9a, D) in- 

 dicates that the sixth segment represents tlie union of the sixth and 

 seventh segments, and that the following segments should therefore 

 receive a higher number, thus erroneously locating the female gono- 

 pore behind the ninth sternite in both cases. This somewhat repeti- 

 tious emphasis of the fact that the female gono})ore is located behind 

 the eiglith (and not behind the ninth) abdominal sternite, is neces- 

 sitated by Balfour-Browne's statement that the opposite view is the 

 one generally accepted by dipterists, and if such is the case, every 

 effort should be made to correct such a widespread misconception. 



Although the Nematocera do not as a rule exhibit a marked tend- 

 ency toward the formation of a postabdomen, many primitive orthor- 

 ihaphous Brachycera do so, since the m.embranous intersegmental re- 

 gion is frequently greatly developed in them, and the sclerotized areas 

 representing the tergites and sternites are much reduced in the seg- 

 ments of the posterior region of the abdomen in female orthorrha- 

 phous Brachycera related to the Eliagionidae (Leptidae). These tend- 

 encies reach their culmination in the female IMiiscoidea (Fig, 9a, 1)), 

 in which the membranous intersegmental regions of the postabdomen 

 are very large, and the sclerotized areas of the tergites and sternites 

 (which may become split longitudinally) are reduced to longitudinal 

 .strips (Fig. 9, E), for strengthening the membranes in wliich they 

 are embedded, and for furnishing supi^orts for the attachment of tlie 

 muscles operating in the telescoping movements of the egg-laving 

 tube formed by the postabdomen. 



The Tenn/nalia of Female Nematocera. The terminalia of the 

 tii)ulid Cli/toroxmm,^ shown in Fig. 9, A, mav be taken to illustrate 

 the ternnnal abdominal structures of a primitive tvpe of Nematocera, 

 altliough the structural details of the terminalia have been more 

 carefiilly worked out in female culicids of the type described later. 



The eighth abdominal tergite or epigyniu'm, H of the tipulid 

 slLOwn m Fig. 9, A, is much reduced in comparison with the ter^ntes 

 of the preceding segments, but the eighth sternite or hvpoovniun", Ss, 

 IS well developed and projects backward below the postgenital se<r- 

 ments. The valves, hg, of the ei,ghth sternite are called the hypS- 

 valvae or hypogynial ^•alves in the tipulids, in which thev form' the 



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