330 



PSYCHE. 



[October 1S92. 



monograph of the Oestridae (1S63), and 

 in die work on the Diptera of the Im- 

 perial museum of Vienna (Denkschr. 

 acad. wissensch., v. 42, p. 108) ; there- 

 fore it is necessary here only to repeat 

 briefly the principal characters, and to 

 discuss those of chief importance from 

 the new standpoint. The terminology 

 employed is the same as-that of earlier 

 authors, so far as known, so that the 

 comparison of our descriptions with 

 those of others may be as easy as pos- 

 sible. Our terms differ from those of 

 other authors only where an understand- 

 ing of single parts made the addition of 

 new terms necessary. This was par- 

 ticularly the case with the chitinous 

 plates forming the epistoma [clypeus.] 

 In the Schizometopa the head is di- 

 vided by a seam or fissure in front and 

 above into two parts, which merge into 

 each other below near the cheeks. This 

 seam is more or less perpendicular to 

 the longitudinal axis of the body, and 

 runs as a curved wrinkle around the 

 upper edge of the antennal prominence 

 and thence downward, generally in a 

 horseshoe shape. Above and outside 

 of the curved seam lie the so-called front, 

 the vertex and ocelli, the compound eyes, 

 and the cheeks ; below and inside the 

 seam lie the lunula with the antennae, 

 the epistoma (which generally deepens 

 above into the antennal grooves and 

 forms below the front edge of the oral 

 cavity) , and on both sides, of the last 

 the vibrissal ridges, reaching down- 

 ward a greater or less distance, or 

 disappearing by abbreviation. Each of 

 these is separated from the clypeus 



by a furrow or seam, extending from 

 the outer half of the antennal groove. 

 The vibrissal ridges usually form at the 

 lower end a small raised or re-entrant 

 angle, pointing toward the middle line 

 of the face, — the so called vibrissal 

 angle, on which as a rule the longest 

 bristles (or the genuine vibrissae) are 

 located. When the clypeus lies in a 

 hollow, the vibrissal ridges bound the 

 facial groove, which must be distin- 

 guished from the antennal grooves, inas- 

 much as the latter may be secondaiy 

 excavations within the former, or may 

 occur alone with a smooth or elevated 

 clypeus and often are united in a single 

 groove (Dexiosoma). The last is 

 always the case when the vibrissal 

 ridges are lacking or abbreviated and the 

 vibrissal angle forms the lower bound- 

 ary of the antennal grooves. Longer 

 bristles are often situated in that case on 

 the outer edge of the antennal grooves, 

 because the latter are identical with the 

 facial groove (Oestromyla) . 



The position of the vibrissal angle 

 has a relation to the lateral end of the 

 curved seam. The latter often ends 

 close to the vibrissal ridges, having a 

 linear form ; or the two ends maj T be 

 mo.e widely separated, enclosing a 

 larger facial area (clypeus-r-vibrissal 

 ridges and antennae) and ending close 

 to the lower edge of the eye with a 

 larger or smaller groove (the bow- 

 groove, facial impression, oblique im- 

 pression, of other authors), by which 

 the upper and lower portions of the 

 cheek [sides of face and cheeks] are 

 sharply separated. If the end of the 



