302 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



it is comnion is shown from tlie fact that Professor Riley bred 20 females 

 from a lot of 1G2 apple-worm cocoons. In these he found great varia- 

 tion in size, some measuring but one-fourth of an inch in length, while 

 others reached one-half. 



Eroughly describing this parasite, we may say that it presents a nearly 

 black appearance above, the under side of the abdomen being honey- 

 yellow. When viewed with a lens, the upper surface of the abdomen 

 is seen to be covered with close punctures, while the thorax is nearly 

 smooth. The legs are reddish yellow with the exception of the middle 

 joint of the hind ]iair, which is black, with a broad yellow ring in it- 

 middle. The hind feet are dusky. The female ovipositor is dark shin 

 ing red. The palpi are pale yellow. 



Cryptus i^ukcius. Say. — Another ichneumonid parasite, belonging 

 to a diffeijut genus from the last two discussed, and known by the above 

 scientific name, was bred from cotton chrysalids, on two occasions or 

 more, in the department last season. It is a very common parasite, and 

 has been often bred in large numbers from the cocoons of the larger 

 Bombycid moths. I have bred no less than 35 individuals from one 

 cocoon of Telea polypJiemus. It is probable that several may occasionally 

 be bred from one chrysalis of Aletia. 



This concludes our list of hymenopterous parasites of the cotton- 

 worm. The remaining live belong to the order Diptera, or two- winged 

 insects. 



The Tachina flies {DijH., family Tacliinide). — Two of these two- 

 winged parasites belong to the family Tachinidae. 



These Tachina flies have much the appearance of the ordinary house- 

 flies, but are usually larger. Their eggs are tough, white, opaque, 

 oval, and somewhat flattened on the side towards the body, to which 

 they are firmly attached by a gum insoluble in water. "With the slug- 

 gish caterpillars these flies have little difiiculty in depositing their eggs 

 when, how, and where they please. They always x)lace them upon the 

 back of the head, or on the first three or four segments of the body, in 

 such a position, in fact, that the caterpillar can in no way reach them. 



The i)arasitic larva, when ready to hatch, eats its way through the 

 egg on the side towards it« victim and burrows into its flesh. They 

 seem endowed by nature with a fondness for nothing but fatty tissue, 

 which teaches them to leave the vital parts of the host alone. When 

 full-bred and ready to transform they do not, as did the last-mentioned 

 parasites, transform within the shell of the insect from which they have 

 obtained their nourishment, but perforate the skin and enter the ground 

 to the depth of from half an inch to two inches. Here they contract to 

 brown oval puparia and remain for a longer or shorter space of time. 

 According to Eiley, th e last brood usually winters in these puparia. The 

 following spring the fly issuing works its way to the surface of the ground 

 and takes wing. 



These insects are among the most effective parasites of many noxious 

 insects. The Northern army- worm is frequently almost exterminated in 

 localities by Nemoraea leucaniae, Kirkp., and Exorista flaricauda, Kiley. 



The Colorado potato-bug has been killed off in great numbers hyLydella 

 dorypho7-ae, a member of this family, and the Eocky Mountain locust 

 found in Tachina anonyma, one of its most determined enemies. It would, 

 indeed, have been strange, had not at least one species of this family 

 been found among the cotton- vrorms. 



In ]!^ovember, 1878, two specimens of what seemed to be a now species 

 of Tachina were bred from the pupa of the cotton-worm. From these 



