94 Journal New York Entomological Society. t^'o'- ^-^• 



yellow silky hairs. Halteres yellow. Abdomen concolorous with thorax or 

 more greenish, with black hairs, longer on the posterior edge of the seg- 

 ments, fifth segment in male nearly twice as long as fourth on dorsal side, 

 ventrally it is entirely cut away to receive the large hypopygium, which has a 

 pair of yellow processes extending forward one third the length of the fourth 

 segment. Legs usually yellow, middle and hind coxae blackish, tarsi some- 

 what infuscated toward the tip ; front femora with some bristles on the 

 outer and upper side ; hind femora with a long shining area on the inner 

 side, destitute of hairs, extending the whole length ; hind tibia with a narrow 

 shining streak on the hind side, from below the middle to the apex. Wings 

 yellowish, veins yellow on basal half. 



Length, 4 to 5 mm. ; of wing, 3.5 to 4.5 mm. 



This species varies in several ways : the yellow color of the pollen may 

 vary to whitish, especially on the face ; the color of the legs may be con- 

 siderably infuscated, especially on the femora ; the hairs of the front may 

 vary considerably in size ; and the shining spot on the upper part of the face 

 may be absent. As all these variations may occur in a lot taken together, 

 they do not indicate specific differences. 



Larva. — My material is far from abundant, but will allow a comparative 

 description with hians. The larva of subopaca differs in not having the 

 dorsal pigmentation and the black integumental plate below the retracted jaw- 

 capsule. The color is almost white, but the tips of the forks of the anal 

 tube are very black, contrasting more with the general color than in hians. 

 There are no basal filaments from the anal tubes. The proportions of body 

 and tube are about as in hians, but the size a little smaller. 



Pupariuni. — There are faint pigmented spots on the dorsum. The sixth 

 and eighth pairs of prolegs are uniformly large, the last with hooks directed 

 forward ; these two pairs are used in grasping a support while in the pupal 

 period, the anterior five and the seventh being small but with good-sized 

 hooks. The color of the integument varies but is generally light, and in many 

 specimens the macrochaetse of the pupa can easily be seen through the pu- 

 parium — often indeed small hairs as well. The flat or concave region of the 

 anterior end above is strongly marked, and the rudimentary spiracles stand 

 out laterally on the (apparent) first segment, their protruding part divided 

 into three or four processes. 



Distribution. 



Massachusetts: Woods Hole (Melander). 

 Connecticut (Loew). 



New York: Ithaca, at salt pond (Johannsen). 

 New Jersey: several localities (Smith Catalogue). 

 Illinois: Gallatin Co., at salt pond (Packard). 

 Utah: Box Elder Lake (salt). Garfield (brackish seepage ). 

 Promontory Point (brackish spring). 



