64 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 68 



KEY TO NORTH AMERICAN SPECIES OF SPHENOMETOPA 



1. Front at base of antennae as wide as either eye 2. 



Front at base of antenna distinctly narrower than either eye; section of 



fourth vein beyond the bend nearly straight; paraf rental rows not widely 

 divergent below; male with conspicuous smoky spots in the wing, and 

 with the basitarsus of the foreleg expanded into a large triangular seg- 

 ment nebulosa (Coquillett) . 



2. Middle tibia with only a single bristle on outer hind side near middle; arista 



thickened to apex 4. 



Middle tibia on outer hind side near the middle with several bristles; arista 

 thickened on basal three-fifths 3. 



3. Abdomen with a broad black median vitta bordered with white pollen; basi- 



tarsus of foreleg bearing a conspicuous tuft of black hair. 



(male) cocklei (Townsend). 

 Abdomen golden pollinose, with a pair of small bronzed spots on the sides 

 of the first three segments; basitarsus of foreleg without ornamenta- 

 tion (female) cocklei (Townsend) . 



4. Front, including the vitta, conspicuously silvery; thorax black and but thinly 



whitish pollinose (male) tergata (Coquillett). 



Front and thorax densely golden pollinose, frontal vitta brown. 



(female) tergata (Coquillett). 



SPHENOMETOPA TERGATA (Coquillett) 



Araha tergata Coquillett, Journ. New York Ent. Soc, vol. 3, p. 103, 1S95; 

 U. S. Bur. Ent., Tech. Ser., No. 7, p. 127, 1897.— Smith, Ins. of New 

 Jersey, p. 782, 1909. — Thompson, Recherches sur les Dipt6res Parasites, 

 Paris Edition du Bull. Biol, de la France et de la Bclgique, pp. 107-108, 

 figs. XXXII, 116, 1921. 



Euaraba grisea Robiucau-Desvoidy, Townsend, Insecutor Ins. Menst., No. 6, 

 p. 182, 1918 (in error). 



In this species the front is somewhat wider than in the other two 

 North American forms, being 0.36, 0.3G, 0.36, 0.37, 0.37, with an 

 average of 0.364 of the head width in five males, and 0.41, 0.44, 0.44, 

 0.44, 0.46, with average of 0.438 in live females. In the male, the 

 inner orbits are narrower at vertex than at base of antennae; the 

 front, including the vitta, and the face are brilliant silvery pollinose; 

 frontal vitta with barrel-shaped outline; frontal rows suddenly- 

 divergent below; two proclinate orbitals; arista short plumose, 

 thickened almost to apex, penultimate joint not longer than broad. 

 Mesonotum in front of suture, and scutellum, dull black, while pleura, 

 mesonotum behind the suture and apex of scutellum, arc silvery 

 pollinose; scutellum with two pairs of strong marginal bristles, the 

 apicals wanting. Abdomen shining black, with silvery pollen at 

 the lateral basal parts of the first three segments, the fourth with a 

 band of white pollen on basal half; first segment without bristles, 

 intermediate segments with strong median marginals, and fourth 

 with a marginal row. Inner forceps of male genitalia (pi. 1, fig. 4) 

 slightly divergent from near base, somewhat flattended at base, 

 tapering gradually to slender tips, round in cross section; outer for- 



