No. 64] DIPTERA OF CONNECTICUT: MORPHOLOGY 23 



more vertically downward and the long axis of the head makes an 

 angle with the long axis of the body. The occipital foramen, o/, con- 

 sequently takes up a somewhat dift'erent position in the hinder region 

 of the head, which becomes more flattened posteriorly as its surface 

 (including that of the occiput, oc) assumes a position more nearly 

 vertical to the long axis of the body. While the occipital foramen, c>/, 

 is not so centrally located in the anisopodid shown in Fig. 2, K, as it 

 is in the syrphid show^n in Fig. 1,K, the condition exhibited by the 

 anisopodid is somewhat intermediate between that exhibited by the 

 tipulids, etc. (Fig. 1,F), and the higher Diptera (Fig. 1,K), and 

 clearly indicates a modificational tendency in the direction of the 

 higher Diptera. 



The occipital region, oc, of Anisopiis (Fig. 2, K) extends ventrad 

 on each side of the occipital foramen to a point half-way down the 

 sides of the foramen, of, where it merges wath the postgenae, pff, or 

 areas behind the compound eyes. The narrow marginal sclerites la- 

 belled pag in the anisopodid shown in Fig. 2, K, which are homologous 

 with the paragular sclerites of lower insects, are called the parapost- 

 genae by Peterson (1916). 



In the higher Diptera, the hinder region of the head is usually 

 rather sharply differentiated from the anterior region of the head, 

 and its surface is frequently greatly flattened, or it may even become 

 concave, as is the case in the syrphid shown in Fig. 1, K. The entire 

 posterior region of the head is sometimes called the "occiput" in the 

 higher Diptera, but the true occipital region includes only the upper 

 region of the posterior portion of the head, and it is preferable to 

 refer to the entire hinder region of the head as the postcranium (in 

 contradistinction to the "]3recranium") in these insects. The posterior 

 surface of the head usually lies at right angles to the long axis of the 

 body, and the occipital foramen, of, occupies a central location in the 

 postcranium of the higher Diptera (Fig. 1,K). 



Superficial markings of the posterior surface of the head of the 

 higher Diptera may divide it into areas to which various terms have 

 been applied by different writers. Thus, the median sclerite, labelled 

 m in Fig. 1, K (which may extend much further back toward the oc- 

 cipital foramen, of, in some Cyclorrhapha), is sometimes called the 

 occiput by some dipterists. while those who follow Lowne call it the 

 epicephalon, and those who follow Desvoidy call it the cerebrale. 

 Hendel (1928) considers that the occurrence of the "cerebrale" is one 

 I of the chief distinguishing characters of the higher Diptera, as con- 

 trasted with the Nematocera. 



The lateral occipital region, loc (Fig. 1,K), together with the 

 postgenal region, pgr, make up an area designated as the paracephalon 

 or paracephalic plate by Walton (1909) who applies the designation 

 metacephalon to the "gular" region, gu, having adopted most of these 

 designations from Lowne's terminology. 



The area pao (Fig. 1, K) surrounding the occipital foramen, of, 

 is called the parocciput by Peterson (1916). Snodgrass (1928, p. 39) 

 designates this region as the postocciput in lower insects. 



