i 44 CONNECTICUT GEOL. AND NAT. HIST. SURVEY [BuU. 



Small, anterior, lateral cervical sclerites, al of Fig. 6, A and E. 



V occur in some tipulids, mycetophilids, etc., but they are always small 



I and unimportant. The posterior lateral cervical sclerites, labelled j>l 



in Fig. 6, B and C, are of more general occurrence, and are found 



I in some Cyclorrhapha, stratiomyids, tabanids, anisopodids, bibionids, 



mycetophilids, etc. The sclerite, fl, may be free, as in Fig. 6, C, or it) 



may be attached to the anterior margin of the propleuron, as in Fig/ 



6, B. The presternum, frs of Fig. 6, C, forms a ventral cervical 



sclerite in certain Cyclorrhapha, but it is usually absent in the lower 



Diptera. 



In some cases, the character of the neck plates is of considerable 

 value for indicating the relationships of the members of the tribes or 

 subtribes of the families of lower Diptera. Thus, the shape of the 

 lateral cervical sclerites is a feature of considerable importance for 

 distinguishing the members of the subtribe Eriopteraria from the 

 members of the subtribe Claduraria, in the eriopterine tipulids 

 (Crampton, 1925) ; and it is possible that these structures may proA'e 

 to be of value in other families of Diptera. 



3. The prothorax 



The prothorax is greatly reduced in the Diptera; and the pos- 

 terior region of the pronotum exhibits a marked tendency to unite 

 with the mesonotum in the higher Diptera — as is also the case in the 

 higher Hymenoptera. The dorsal and lateral regions of the prothorax 

 are quite closely" united in the Dipt^■^'" ^" g-o»^o«^i, i^^ai ti^o =.j-^,.,ir. 

 region usually rWains sepovo^^o'^i ^'i-om the pleural region in the lowe 

 Diptera. In certain Mycetophilidae, Bibionidae. Stratiomyidae and 

 Tabnnidae, however, the principal sternal sclerite, or basisternum, 

 Z>.s- (Fig. T), B), is connected with the episternum, (?5, by a pre-coxal 

 bridge, fc^ or sclerotized band extending in front of the coxa, cx^ 

 from the sternal to the pleural region of the prothorax ; and the arch 

 formed in this fashion probably gives added rigidity to the sclerites 

 which it connects. 



The Pronotum. The pronotum of the Diptera, like that of cer^ 

 tain Hymenoptera and Mecoptera, is divided into an anterior region, 

 or antepronotum, a/pn. and a posterior region, or postpronotum, pjm 

 (Fig. 6, A,B,C, D and E). The antepronotum, apn.. is best develop- 

 ed in the tanyderids, certain tipulids, etc., but it tends to become; 

 much reduced in the higher Diptera, in which the postpronotum, pfn 

 (Fig. 6, C) increases in size, and becomes closely united with the 

 mesonotum (Fig. 6, E). The postpronotum, ppn of Fig. 6, C. is 

 usually referred to as the humerus, or the humeral callus of the 

 "mesonotum" in the higher Diptera, although Hammond (1881) long 

 ago i^ointed out that in the blowfly the muscles attached to the 

 "humeral callus" are prothoracic, not mesothoracic. The postpro- 

 notum, ppn of Fig. 6. D, is usually incorrectly called the prothoraci( 

 "epimeron" in mosquitoes (see Freeborn, 1924). In the sheep tick 

 (Fig. 6, F) the pronotum becomes indistinguishably united with the 



