706 REPORT UNITED STATES GEOLOGICAL SURVEY. 



Two parasites live iu this micrognster, RoclieriaiJerjndchraawd Ghjplie 

 I'iridesccns, belonging to the Chalcid family of ichneumons. Walsh says : 



We now know that of 145 ichneumon-flies, promiscuously taken, that had depre- 

 dated on the army-worm, 27, or only 18 per cent., j)erished by Chalcia flies. 



Iclmeumon leucaniw Fitch. — Dr. Fitch has given an account of another 

 ichneumon. 



This parasite resembles a small wasp, nearly half an inch loujr, of a bright rust-red 

 color, its wings smoky, its breast black, and also the middle of its back, where is a 

 small bright sulphur-yellow spot, which is the scutel. The anteunaj have a milk- 

 white band on their middle, below which band they are rush-red, and above it black. 

 There are two narrow bands also on the back of the abdomen, placed on the fourth or 

 fifth .joint, and the slender peduncle of the abdomen is also black. Mr. Sanborn has 

 raised this same species, as also another ichneumon, which we describe. 



Ichneumon species. — Ichneumons of this genus are rather slender- 

 bodied ; the abdomen long oval. AVings not much longer than the slen- 

 der antenuiP, which in turn are a little more than one-half the length of 

 the whole body. The legs and joints of the feet are also slender. The 

 ovipositor of the female is not apparent; her eggs are pedunculated, 

 Laving a general likeness to those of the genus Ophion. 



The species before us i^ black and yellow. Head : face square, yellow ; a daik line 

 borders the base of the antenme, which arc rusty, the first joint yellow, and the ends 

 dusky. Head behind the antenutc black. Thorax black ; above on its first joint, or 

 prothorax, a yellow transverse elliptical. On the second joint which carries the fore 

 wings are two yellow stripes forking toward the head. fScutellum yellow ; another 

 transverse elliptical yellow spot behind. Third joint of thorax yellow above, black 

 beneath. Legs: first and second pairs yellow, reddish above on first joint. Third pair 

 black at base; second joint yellow; third, or femur, black ; fourth, or tibia, black at 

 tip. Tavsi, or toes, marked with black. 



The elbowed abdomen black at base, the elbow yellow. The next three yellow 

 joints with a narrow black strip on the front edge, the hinder edge of the ring tinged 

 with reddish. Last three rings black. 



Our last parasite is a fly, or species of the Tachina family, that Mr. 

 Shurtleff and Sanborn have both raised from the army-worm, and I find 

 it to be identical with the si)ecies that attacks the worm in the West. 



Exorista leucanuc Kirkpatrick (Senometopia militaris Walsh). — This 

 genus resembles in form our common house-fly. The thorax is usually 

 striped longitudinally, and the whole body coveired with large hairs. It 

 flies low in sunny spots in woods, with a loud buzzing noise. We copy 

 Mr. Walsh's description, and select some interesting information he gives 

 us about its habits : 



Length, .25 to .40 inch; the females not exceeding .30 inch. Face silvery, with lat- 

 eral black hairs only on the cheeks, at the top of which is a black bristle. Front 

 golden olive, with a black central stripe, and lateral black convergent hairs. Occiput 

 dusky. Labium, brown, with yellowish hair. Maxipalps, rufous. Eyes, cinnamon- 

 brown, covered with very short dense whitish hair. Auteuu;e, two basal joints, black, 

 with black hairs ; third joint flattened, dusky, and from two and a half to three times 

 the length of the second joint; seta, black. The entire hinder part of the liead Cov- 

 ered with dense whitish hair. Thorax glabrous, bluish-gray and lighter at the sides, 

 with four irregular black vittir, and black hairs and bristles. Scntcl, reddish-brown, 

 whitish behind, glabrous, with black hairs and bristles. Pectus, black, glabrous, with 

 hairs and lateral bristles ; legs, black, hairy ; thighs, dark cinereous beneath ; pur- 

 villi, cinereous. Wings, hyaline; nervures, lirownish ; alulio, opaque greenish-white. 

 Abdomen, first joint black ; second and third, opalescent in the middle, with black and 

 gray, and at the sides with rufous and gray; last joint, rufous, slightly opalescent at 

 base with gray; all with black hairs and lateral bristles. 



Beneath, the first joint is black ; the others, black marginal with rufous, all with 

 black hairs. Iu the male, the space between the eyes at the occiput is one-seventh of 

 the trausversie diameter of the head ; in the female, it is one-fourth. 



Some i)upacases of this fly before me are a little more than a quarter 

 inch long ; cylindrical ; rounded at each end. The last segment, barely 



