NO. 1487. NORTH AMERICAN DIGGER WASPS— FERNALD. 297 



EXTERNAL ANATOMY. 



Head. — The hypog-nathous head i.s hirgo, ])roadcr than long-, giving 

 it a transverse oval or somewhat (Quadrangular (uitline when viewed 

 from above. The compound eyes are large and extend from the top 

 of the head almost to the base of the mandibles. Viewed from in 

 front they form nearly half of the width of the head, while from the 

 side they occupy a greater proportion, the cheek which lies behind the 

 eye being- at its widest place rarely more than half the width of the 

 eye. The anterior and lateral margins of the eye are quite sti-aight, 

 but in l\oterosp}iex this org-an near the top extends toward the middle 

 of the head somewhat, so that the two eyes are nearer each other at 

 the vertex than a little lower down. In some species the two eyes 

 converge somewhat below, particular!}^ in the males, till their distance 

 apart near the middle of the clypeus is less than on a line drawn 

 through the posterior ocelli. (Plate VI, tig. 1.) 



The clj'peus occupies the lower portion of the front of the head 

 between the compound eyes and extends upward nearl3"to the antennae. 

 Its form differs in the different subgenera, but is more or less trian- 

 gular, the truncated apex being above. It is somewhat convex and 

 extends to varj-ing distances below the eyes in different species. The 

 outline of its anterior edge also varies and is made use of in the deter- 

 mination of the subgenera. (Plate X, tigs. 22-26.) 



• On each side of the cl3"peus is a wedge-shaped extension downward 

 from the f rons, separating the upper part of the clypeus from the com- 

 pound eye. The dorsal edge of the clypeus is indicated by a trans- 

 verse suture a short distance below the insertion of the antennae. In 

 some cases the lateral sutures are continued upward as grooves of the 

 f rons which converge and meet between the antenna leaving a triangle 

 above the truncated apex of the clj'peus, which when the suture 

 Between it and the clypeus is not pronounced seems to be a part of the 

 latter plate. From the junction of these two grooves between the 

 antennse a median groove (the frontal suture) extends toward the ver- 

 tex to the median ocellus where it divides, a branch passing lateral to 

 the ocellus on each side. Behind the ocelli a transverse groove con- 

 necting these branches is sometimes perceptible, thus inclosing the 

 ocelli in a triangular area. Sometimes, also, traces of the frontal 

 suture may be found behind the median ocellus and between and even 

 behind the lateral ocelli. 



The frons then may be regarded as extending upward from the 

 clypeus to the ocelli, with a downward extension on each side of the 

 former, and an upward extension on each side of the latter. Near the 

 frontal suture, close together, and a short distance above the clypeus 

 are the antennal insertions. The frons as a whole is usuall}^ sunken 

 below the level of the e3"es and clypeus, giving the front of the head 

 as viewed from above a somewhat excavated appearance. 



