No. 64] DIPTERA or CONNECTICUT: MORPHOLOGY 17 



the Diptera (as is done in the lower insects), and the term peristoma 

 may then be used to refer to the general ''oral margin" or border ol" 

 the "oral cavity". The cavity into which the base of the proboscis is 

 retracted should be called the subcranial cavity and its margin should 

 be called the subcranial margin, however, since the true oral cavity 

 is a wholly different region in relation to the mouth parts, and it is 

 therefore incorrect to refer to the cavity into which the base of the 

 proboscis is withdrawn as the "oral cavity", or to refer to its margin 

 as the "oral margin". 



The frons or front (Trif and fv of Fig. 4, J, etc.) extends from the 

 fronto-clypeal suture (or from a line drawn across from one frontal 

 pit to the other) to the frontal suture (formed by the arms of the Y- 

 shaped ej^icranial suture) in the lower insects. In the Diptera. how- 

 ever, the true frontal suture, which contains the median ocellus in its 

 posterior angle, is apparently absent, despite the fact that Peterson 

 (1916) and others regard the ptilinal suture, j>tc of the dipteran shown 

 in Fig. 4, J, as the frontal suture in the higher Diptera, and interpret 

 the fronto-clypeal suture, /cs, bordering the postclypeus or epistoma 

 posteriorly in the Diptera shown in P'ig. 1, H, etc., as the frontal 

 suture in the lower Diptera. Some feature other than the frontal 

 suture must therefore be used to demark the posterior limits of the 

 frons in the Diptera, and on this account the position of the median 

 ocellus has been accepted for this purpose, although it has also been 

 suggested that the bases of the antennae would make ideal landmarks 

 for delimiting the frons posteriorly were it not for the fact that the 

 median ocellus is typically borne in the postero-median region of the 

 Irons in lower insects, and the region between the bases of the an- 

 tennae and the median ocellus (i.e., fv of Fig. 4, J) must therefore 

 also belong to the true frons in the Diptera. Walton (1909) limits 

 the frons or front to the "space between the eyes in dichoptic flies, 

 limited by the upper margin of the head and a line drawn through 

 the root of the antennae," but if the frontal region of the Diptera is 

 to be homologized with the frontal region of lower insects, it must 

 also include the region m/ below the antennae down as far as the 

 frontal pits in both cases. Since some other designation should be 

 used for the region called the front in Walton's definition of the frons 

 of the higher Diptera, the term "postf acial area" has been suggested as 

 a possible substitute. 



The points of attachment of the antennae divide the frons into a 

 preantennal region of the frons and a postantennal region of the frons 

 {prf and jjof of Fig. 1, G and L, etc.) to which the terms prefrons 

 and postf rons might be applied, although the boundaries of these re- 

 gions do not coincide quite exactly with those of the regions called 

 the prefrons and postf rons by Hendel (1928) and de Meijere (1916), 

 who have attempted to apply Berlese's terminology to the areas of the 

 head in the Diptera. 



The lunula, frontal lunule, or frontal crescent, is an oval or cres- 

 centric area, lu of Fig. 4, J, occupying the space between the bases of 

 the antennae and the hinder angle of the ptilinal suture, ftc^ in the 

 Schizophora. Townsend (1908, p. 21) considers that the lunula is 



