82 COXXECTICUT GEOL. AND NAT. HIST. SURVEY [BllU. 



fleshy lobes, but in the typical tipulids they are slender, pointed, 

 rather strongly selerotized structures like those of the tipulid shown 

 in Fig. 9, A, and form the dorsal valves of the egg-laying apparatus 

 of these Diptera, This type of one-segmented cerci, bearing lateral 

 ridges or flanges, is remarkably similar to the one-segmented cerci of 

 the mecopteron Boreus, and the similar modificational tendencies ex- 

 hibited in the Mecoptera and Diptera in most of the structures of the 

 body clearly point to a mecopteroid ancestry for the Diptera. 



It is ver}- surprising that the cerci of the Nematocera are usually 

 com loosed of but one segment, even in the females, in which the cerci 

 are better developed than in the males; but some female Nematocera 

 have retained the two-segmented condition typical of most Mecoptera, 

 as is the case in the fossil tanyderid Macrochile figured in Plate I of 

 the paper by Cramplon (192Gb), and in certain female mycetophilids 

 such as Macrocera, etc. The two-segmented cerci may be retained 

 even in such "higher'' forms as the rhagionids (leptids) and stratio- 

 myids (Fig. 9, G), however, and in the latter insects they are slender 

 structures very suggestive of the cerci of typical Mecoptera. Accord- 

 ing to Metcalf (1921), the cerci are also two-segmented in the syrphid 

 Chrysogaster pulchella. 



The characters furnished by the terminalia of female mosquitoes 

 are used by Gerry (1932), Christophers (1923) and others for dif- 

 ferentiating the genera and even the species of the Culicidae; and it 

 is quite possible that similar characters wvA.y prove to be of some 

 taxonomic value in other Nematocera as well, since the culicids are 

 quite primitive Diptera and are fairly typical Nematocera. The 

 parts have been studied quite thoroughly m female mosquitoes, and 

 the structural details presented by the female culicids wall serve to 

 illustrate the structural details of a typical female nematoceran in 

 the following discussion. 



As is shown by Christophers (1923) in female mosquitoes, the 

 common oviduct, the spermathecal duct, and the terminal pouch of 

 the mucous gland, open into the so-called atrium, at of Fig. 9, C, or 

 genital chamber situated between the eighth and ninth abdominal 

 sternites. The atrium, at, is bordered by a preatrial sclerite, pra. 

 belonging to the eighth sternite, and a postatrial sclerite, poa. be- 

 longing to the ninth sternite; and these two sclerites form the peria- 

 trial sclerites. Christophers calls the area ins (which frequently bears 

 setae, etc.) the insula, and designates the area co as the "cowl", while 

 the plates ap, which are apparently parts of the ninth sternite, are 

 called the atrial plates by him. 



The composite plate, pgp, which may contain the eleventh, and 

 tenth sternites according to Gerry (1932), is called the postgenital 

 plate by him. The ninth and tenth tergites are represented by nar- 

 row transverse sclerites in the lower culicids, but the tenth tergite 

 becomes atrophied in the higher culicids. The cerci, ce, are com- 

 posed of a single segment, and are broad lobe-like structures in the 

 typical culicids. 



The Terminalia of Female Orthorrhaphous Brachycera. In the 



