176 



PSYCHE. 



[November 1891. 



A PARASITE OF THE FALL WEB-WORM. 



BY C. H. TYLER TOWNSEND, LAS CRUCES, N. M. 



In this vicinity the cottonwoods 

 {Populus fremontei') begin to be in- 

 fested with the Fall Web-worm {Hy- 

 fhantria cunea) about the first of July. 

 On July 28 I placed an entire nest of 

 good-sized web-worms in a breeding 

 cage. Aug. 19 quite a number of 

 moths had emerged, and one specimen 

 of the Tachinid parasite described 

 below. The earth was full of the web- 

 worm cocoons and pupae, only a few 

 stray ones having been formed in the 

 leaves and twigs. The moth is the 

 pure, snow-white form, with the thighs 

 yellowish. Aug. 25 three more speci- 

 mens of the Tachinid were secured. 

 The following is a description of the 

 latter. 



Meigenia hyphantriae n. sp. $ . Silvery- 

 cinereous, and black. Eyes dark brown, ex- 

 tending not quite so low as the vibrissae, 

 thinly hairy on lower portions; front at 

 vertex about one-third the width of head, a 

 little wider at base of antennae, somewhat 

 prominent, silvery on sides with a cinereous 

 shade; frontal vitta narrow, not one-fifth the 

 width of front, dark brown, the prongs on 

 sides of ocelli rather faint, ochreous ; frontal 

 bristles moderately strong, three posterior 

 ones inclined backward, others inward, 

 decussate except the divergent lower ones 

 which extend as far down as base of third 

 antennal joint; two orbital bristles on each 

 side; face and cheeks silvery, face strongly 

 receding, facial depression rather "wide, 

 facial ridges bristly for some distance above 

 the vibrissae which are decussate and in- 

 serted considerably above the oral margin; 



sides of face moderately wide, bare; cheeks 

 moderately narrow, bare, except bristles on 

 lower border; antennae a little shorter 

 than face, first two joints rufous, first joint 

 very short, second slightly elongate, third 

 narrow, black, rufous at base, about three 

 times as long as the second; arista black, 

 microscopically pubescent, rather long, 

 thickened for one-third its length, apparently 

 2-jointed, the second joint short; proboscis 

 rufous, but little extended, fleshy, apparently 

 very short, labella large, flavous or rufous; 

 palpi well developed, slender, nearly cylin- 

 drical, flavous or rufous, black hairy; occiput 

 gray or cinereous, with whitish hair, except 

 a wide black vitta from vertex to center, 

 orbital margins fringed with black bristles. 

 Thorax narrower than head and abdomen, 

 widest in front, silvery, shaded with cinere- 

 ous above, with two narrow well-defined 

 black vittae and a lateral interrupted one, 

 bristly and hairy; scutellum cinereous, with 

 an apical very short, weak, decussate pair of 

 bristles, a sub-apical decussate pair of macro- 

 chaetae extending to base of third abdominal 

 segment, two lateral and a discal pair of 

 macrochaetae ; humeri and pleurae silvery, 

 bristly. Abdome?i rather conical in outline, 

 short, stout, first segment a little shortened, 

 macrochaetae only marginal ; first segment 

 black, without macrochaetae ; second and 

 third broadly silvery at base, blackish on 

 posterior border; second with a median pair 

 of macrochaetae, and a single lateral one; 

 third with eight macrochaetae ; anal more 

 yellowish at base, armed with macrochaetae 

 and bristles above and below. Legs black, 

 coxae and femora silvery, tibiae slightly 

 so, femora and tibiae bristly, hind tibiae 

 with a fringe of bristles on outer edge; claws 

 and pul villi a little elongate. Wiiigs rather 

 broad, longer than the abdomen, without 



