No. 64] DIPTERA OF CONNECTICUT I MORPHOLOGY 43 



disphicemeiit of the sclerites, forcing it to follow a zigzag course in 

 the higher Diptera. The suture extending upward from the dorsal 

 articulation of the prothoracic, or metathoracic coxa, marks the divi- 

 sion of the pleuron of these segments into an episternal and epimeral 

 reigion, so that the dorsal articulation of the coxa is of value for 

 determining the anterior extent of the epimeral region when the 

 epimeron is not clearly dift'erentiated. 



The halter is attached to the lateral margin of the metanotum, 

 and its basal attachment is therefore of value for indicating the 

 position of the metanotum when this region is greatly reduced. The 

 small sclerites labelled aha in Fig. 6, A, C and E, are situated at each 

 end of the transverse suture, ts^ and in most instances serve to indicate 

 the position of the suture even when it shifts about so greatly that 

 it might be mistaken for some other suture. The significance of the 

 other landmarks of the thorax will be discussed later 



2. The neck 



The cervix, or neck region (Fig. 6, A, B, C, D, etc.), is largely 

 formed as a modified anterior portion of the prothorax (a portion 

 of the labial segment may form a certain of the neck plates, also") 

 situated between the head and the more strongly sclerotized region 

 of the prothorax. The flexible membranous walls of the neck permit 

 considerable freedom of movement of the head, while the cervical 

 sclerites, or cervicalia, embedded in the membranous walls of the 

 npplr. sprv-o fr, ciii^i^r.T'f +K^ Kanrl. and fumish points of attachm^ent for 

 certain muscles extending to the Kaj^d reo-ion, 



Loew (1862) calls the neck the ''collum", and applies the designa- 

 tion "cervix" to the postero-dorsal region of tlie head, corresponding 

 to the region called the cerebrale by other dipterists. Coleopterists 

 likewise apply the designation "'cervix" to the postero-dor.-al region of 

 the head in beetles; and the membranous neck region behind the head 

 is sometimes referred to as the eucervix, in order to avoid confusion 

 in the application of the term cervix. ]\Iodern investigators, however, 

 usually restrict the designation "cervix" to the neck region, behind 

 the head, and this usage will doubtless become the generally accepted 

 one. 



The lateral cervical sclerites, or laterocervicalia, Ic of Fig. 6, are 

 the large lateral plates of the neck, which send forward a slender, 

 anterior head-bearing process, or cephaliger, eg, articulating with 

 the occipital condyles, and furnishing supports for the head. The 

 lateral cervical sclerites are the principal plates of the neck region, 

 and are greatly elongated in some tanyderids and tipulidt^. Each of 

 the lateral neck plates, Jc of Fig. 6, D, may send downward a medio- 

 veiitral extension, which joins a similar extension from the opposite 

 side of the neck, in the mid-ventral region; and since such medio- 

 ventral prolongations of the lateral neck plates occur in the simuliids, 

 chironomids, dixids, corethrids, and culicids, this feature may be of 

 some phylogenetic significance, since these insects are undoubtedly 

 very closely related. 



