AMERICAN DIPTERA. 295 



is sometimes only suggested by a slight opake-brown depression ; ven- 

 eral lobe large, yellow, often visible from above (Fig. 49). Legs, 

 except coxae and apices of tarsi, yellow ; femora sometimes discolored 

 above, moderately thickened, with all outer surfaces as well as those 

 of tibiae, more or lese silvery; spines weak. Wings grayish with 

 colored stigma (Fig. 133). Length, 4.5-5.3 mm.; wings, 5.0-6.3 mm. 

 9 . Similar, with front much narrower than face, entirely silvery, 

 with a fine median black line. Mesonotum in some seem to be more 

 grayish with three faint median brown stripes, also the scutellum is 

 more grayish in some. Base of ovipositor brown or yellow, quadrate, 

 nearly cubical, abruptly terminated by the short stout yellow ovi- 

 positor, which is hardly longer (Figs. 50-51). 



This species is not easily confused with any other on ac- 

 count of its large size, the subopake abdomen with its white 

 pollinose margins and fascia?, and yellow legs. P. houghii 

 Kert. {lateralis Walk), has the abdomen polished without 

 white fasciae. 



Described from Massachusetts and Pennsylvania, and is 

 also reported from New Jersey (1899 Smith 665) and 

 Canada (1901 Chagnon 13). I have examined specimens 

 from Hanover, N. H., 1 c? 1 ; Hyannisport, Mass., 1 d 1 , (Fig. 

 11, 49) ; East Walpole, Mass., 1 & ; Winnapauk, Ct., 1 & 

 (all by Johnson, B. S. N. H.); Fall River, Mass. (1 9, 

 Easton, B. S. N. H.); Ithaca, N. Y. (1 &, Fig. 135, 

 coll. Banks); Sea Cliff, Long Island (3 cfs, Fig. 133, coll. 

 Banks); Swarthmore, Pa. (1 9 , Fig. 134, Cresson, A. N. S.); 

 Falls Church, Va. (3 9s, Figs. 50. 51, coll. Banks); Black 

 Mountains, N, C. (5 cfs, Fig. 136, 2 9 s, coll. Banks). Taken 

 in May, June and July. Those taken in May seem to have 

 the antennas brown to black, and the femora more discolored. 



This is about the largest known North American species 

 of the genus. The variation seems to be confined to the 

 coloration of the antennae and femora, although the base of 

 ovipositor is sometimes rather less developed, losing its 

 quadrate form. I cannot separate the forms with black 

 antennae, from the others specifically, and seem to be identi- 

 cal although a little smaller. I have before me two males 

 which show some abnormalities in the venation. One from 

 Ithaca (Fig. 135) has an angular bend in the ultimate section 

 of fourth vein indicating a rudiment of an appendage ; this 



TRANS. AM. ENT. SOC, XXXVI. JANUARY, 1911 



