No. 64] DIPTERA or CONNECTICUT: MORPHOLOGY 49 



continued in the posterior margin of the wing (as the so-called axil- 

 lary cord). 



Two extremely interesting modifications of the scutellum are 

 shown in Fig. 7, A and C. In the South American stratiomyid Di- 

 cranojjhm'a furcifera (Fig. T, C), the scutellum, sl^ is prolonged over 

 the top of the abdomen as a slender forked process extending almost 

 to the tip of the abdomen; and in other stratiomyids, diopsids, etc., 

 the scutellum bears long pointed spines and similar processes. The 

 most amazing modification of the scutellum, however, is exhibited by 

 the lauxaniid (or celyphid) fly, Celyphus ohtectus, shown in Fig. 7, A, 

 in which the broad, hemispherical scutellum, .s7, extends over, and 

 largely conceals the abdomen, giving these flies somewhat the appear- 

 ance of tortoise beetles, or scutellerid Hemiptera ; and this resemblance 

 is sometimes heightened by a gleaming iridescence of the entire thor- 

 acic region. 



The postscutellum, or postnotum, fsl of Fig. 6, is the posterior- 

 most plate of the notum. It is hugely developed in most of the lower 

 Diptera, but in some of the higher Diptera, such as the tabanids, 

 sheep ticks (Fig. 6, F), etc., its external surface is considerably re- 

 duced, although the internal phragma, or postphragma, wdiich it 

 bears (i. e., the internal, transverse, shelf -like structure for muscle 

 attachment), is greatly developed in the tabanids, and forms one of 

 the most conspicuous internal features of these insects. 



The postscutellum, or postnotum, fsl^ is divided into a median 

 region or mediotergite, mt^ (Fig. 6), and two lateral regions (one 

 oxx «.ooh side) called the pleurotergites, ftg^ which form the postalar 

 arches, or bridges conneciing me meaian roo-ion of the postscutellum 

 with the epimeral region of the pleuron. The pleurotergite is fre- 

 quently subdivided into an upper and lower region known as the 

 superior and inferior pleurotergite, syt and ipt of Fig. 6, A and C, 

 which are called the anapleurotergite and katapleurotergite by Young 

 (1921). These designations are somewhat long and cumbersome, and 

 might be shortened to "anatergite" and *'katatergite" if it is desirable 

 to designate the regions in question by a single term. These areas 

 are of some importance in the classification of the Tipulidae, etc. 



The subscutellum, ssl of Fig. 6,C, is an area of the mediotergite, 

 mt^ (a median region of the postscutellum) situated immediately be- 

 low the scutellum, 6??. It is usually concave in the muscoid flies, but, 

 as is pointed out by Malloch and others, it becomes strongly convex in 

 the tachinids, and is a character of considerable importance for dis- 

 tinguishing them from most of the muscoid flies. Curran (1924, p. 

 167) calls attention to the occurrence of this sclerite in the Stratiomy- 

 idae, Syrphidae and Tachinidae (including the Dexiidae) and stresses 

 its importance as an indication of the fact that the syrphids and 

 tachinids may have descended from the Stratiomyidae. There is a- 

 very strong possibility, however, that the syrphids, etc., were descend- 

 ed from ancestors like the bombyliids and nemestrinicls, which, with 

 the mydaids, asilids, etc., appear to lead back to a therevid ancestry 

 (rather than a stratiomyid ancestry), and too much weight should 



