6 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY 
area imperfectly separated off by the frontal suture, it shows no 
division into parts. This undifferentiated area must then be arbi- 
trarily divided into regions which will be of taxonomic value. 
Posterior orbit: a narrow band included between the posterior margin 
of the eye and the row of cilia immediately behind it (PI. 2, fig. 11, 
peo.). 
Vertex: an imaginary line between the dorsal inner corners of the 
eyes (PI. 2, fig. 11, vt.). 
Front: the area between the eyes from the vertex to an imaginary 
line drawn parallel to it through the base of the antennae (PI. 1, fig. 1). 
Ocellar plate or Triangle: a triangular area at the upper part of the 
front which bears the ocelli. Its vertex is directed downward and its 
sides marked by depressions in the chitin (PI. 1, fig. 1, ot.). 
Frontal vitta or Frontalia: the dark central band which extends 
upward from the dorsal part of the frontal suture and, dividing at the 
apex of the ocellar triangle, forms two short arms which extend along 
the sides of the triangle and end near the base of the vertical bristles. 
Below the ocellar triangle its sides are paralleled by the frontal bristles 
<P1. 1, fig. 1). 
Parafrontals or Genovertical i^late: those parts of the anterior surface 
of the head which are bounded above by the vertex, on their sides by 
the upper eye orbits and sides of the frontal vitta, and basally by 
faintly impressed lines extending from the points where the sides of the 
vitta join the frontal suture or slightly below, to the eyes. This plate 
bears the frontal bristles, and in females the orbitals as well (PI. 1, 
fig- 1, vfl.). 
Genae: the downward continuations of the parafrontals which are 
bounded on the sides by the lower eye orbits and the arms of the frontal 
suture, and basally by the transverse impressions (PL 1, figs. 1, 6, ge.). 
Transverse impressions: somewhat impressed areas just beneath 
the genae, bounded inwardly by those portions of the arms of the 
frontal suture below the corresponding parts of the genae. They are 
widest at this part, but become narrower laterally and extend to the 
base of the posterior eye orbit (PI. 1, figs. 1, 6, ti.). 
Cheeks: those hairy areas which lie beneath the transverse impres- 
sions and are bounded basally by the lateral margins of the mouth and 
posteriorly by lines drawn from the lateral ends of the transverse 
impressions to the abrupt downward turns of the frontal sutures and 
by the continuation of the latter from this point to the mouth margin 
(PI. l,fig. 1; PI. 2, fig. 11, c). 
