16 COIs^NECTICUT GEOL. AND NAT. HIST. SURVEY [BuU. 



tion of the '"inner" or posterior linino; of the L^brum, and since it is 

 merely a modified j^ortion of the labrum, it is not necessary to refer to 

 the Labrum of higher Diptera as the ^'habrum-epipharvnx" as though 

 it were a composite structure formed by the union of a distinct labrmn 

 and epipharynx. The posterior limits of the labrum may be marked 

 by a clypeolabral suture, but in most insects the most constant land- 

 mark indicating the posterior limits of the labrum is furnished by the 

 position of the tormae, or hinge-like thickenings (one on each side) at 

 the base of the labrum, on the "inner'' or posterior surface of the upper 

 lip. The sclerites which are supposed to represent the tormae which 

 have migrated to the anterior surface of the head capsule in certain 

 Diptera, are probably secondary formations, like those occurring in 

 the anteclypeal region of the orthopteroid insects, such as GryUotalpa, 

 SynterTnes, etc. 



The clypeus, d, is the region betAveen the labrum and the frons: 

 and IS demarked anteriorly by the tormae, while the posterior limits 

 are demarked by the fronto-clypeal suture, or bv a line drawn across 

 from one frontal pit. />, to the other (Fig. 1, G) when the fronto- 

 clypeal suture is absent. 



In orthopteroid insects such as GinjUm, St/ntermes, etc., the 

 clypeal region is divided into an anteclypeus and a postclvpeus (or 

 epistoma), and the sclerite labelled ac in the Diptera shown in Fig. 

 1,L, Fig. 4, A, B, E, J, etc., may possibly be a sclerite of the anteclyp- 

 eal region=^ serving to support the fulcrum, fu. which is attached' to 

 It m such Diptera as the ones shown in Fig. 4, B, E, etc. Since the 

 anteclypeus is merely an anterior region of the clvpeus it is not entirely 

 incorrect to refer to the sclerite ac as the ''clypeus"' (as is done by 

 niany dipterists), although it is more accurate to call it the ante- 

 clypeus Hendel (19:?8) and de Meijere (1916a) call it the "prela- 

 brum; (although it is postlabral in position), while Peterson (1916) 

 calls it the "tormae" since he thinks that the tormae migrate to the 

 anterior surface of the clypeal region to form the sclerite in question : 

 but it IS much more probable that the sclerite in question in the Dip- 

 tera IS formed by the distinct anteclypeal sclerites such as those found 

 in some termites, mole crickets, and other orthopteroid insects de- 

 scribed by Crampton (1932)— see Plate 4, Fig. 1, Plate 6, Fig. 20. etc. 



The narrow marginal sclerite, 2Joc of Fig. 1, B and L, Fio- 3D 

 etc., corresponds in a general way to the sclerite called the post?iypeus 

 or epistoma m the orthopteroid insects, and in fact the designation 

 epistoma is applied to the region poc of Fig. 4, J, by some dipterists 

 although the term epistoma may include a greater area than the post- 

 ciypeal region according to other dipterists. Thus. Smith (1906) 

 dehnes the epistoma in the Diptera as "'that part of the face between 

 tlie front and the labrum; the oral margin and an indefinite space im- 

 mediately contiguous thereto and so equivalent to peristoma,*" and 

 then clefanes the peristoma as ''the border or the mouth or oral maro-in 

 m Diptera; sometimes used as equivalent to epistoma." It is prefer- 

 able to restrict the term epistoma to the post clypeal region, poc, in 



*(In certain muscoids such as Calliphora, etc., an interclypeus. or sclerite between the 

 anteclypeus and postclypeus, is formed just behind the anteclypeal sclerite ) 



