TACHINA ALETIAE. 203 



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 JExorista flavicauda, Eiley. 

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

 doryphorae, 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- worms. 



In November, 1878, two specimens of what seemed to be a new species 

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

 specimens Professor Eiley has described the species, in a recent number 

 of the Canadian Entomologist, as Tachina aletiae, n. sp., as follows; 



3. TACHINA ALETIAE, n. sp. Length, 8 mm . Black; head golden, facial depression 

 silvery, space between the eyes and the frontal stripe about equal to the breadth of 

 the stripe, bristles of the head black, the pubescence behind and beneath the eyes 

 white ; antennae blackish, palpi testaceous. Eyes at a moderate distance apart, thinly 

 pubescent; front moderately prominent; third joint of the antennae three or four 

 times the length of the second joint. Thorax and the second and following abdominal 

 joints more or less ashy, the thorax with four or five longitudinal black stripes. Wings 

 subhyaline. Legs black, with a piceous tinge ; tarsal cushions yellowish. Scutellum 

 and the sides of the first, second, and third abdominal joints sometimes tinged with 

 reddish-brown. No strong bristles on the first and second abdominal joints above. 



Described from two specimens reared in November, 1878, from the pupa of Aletia 

 argillacea. 



During the season of 1879 many of these parasites have been bred. 

 The latter part of July Mr. Trelease forwarded a quantity of parasitized 

 larvae from Dawson's Station, Ala., with the following note : 



JULY 24, 1879. 



I mail you to-day a box containing some 95 pupae and webbed-up larvae of Aletia. 

 * * * I find nearly one-half of the larvae from one-third to two-thirds grown bear- 

 ing small white eggs on their backs. (It is only for the last few days that I have no- 

 ticed this, but it has probably been the case with this entire third brood.) These 

 eggs are of two sizes. The larger are usually, perhaps always, deposited singly on the 

 dorsum of one of the thoracic segments of the larva, and placed transversely or ob- 

 liquely. They are elongated, oval at the two ends, but more often bluntly rounded. 

 Their length averages about 8 mra , their breadth 2 mm . They are very slightly flattened 

 on the surface by which they are attached. Sometimes, when no egg can be seen, a 

 discolored mark of the size and shape of the egg is seen on the back of the larva; in 

 other cases a discoloration below the skin of the thorax appears to show the upresence 

 of a parasite larva. The smaller eggs are also white, and measure about 6 mm by 2 mm , 

 from which you will see that they are broader proportionally, and consequently more 

 oval than cylindrical. They are slightly more flattened on the under surface as a 

 rule. These are deposited on the side and back of the head and thoracic segments, 

 and vary, in the cases so far noticed, from one to four in number ; sometimes, where 

 there are several, being scattered almost in contact with each other. 



These eggs were fastened very firmly to the back of the larvae, and 

 were all so placed that the victim could by no exertion reach them with 

 its jaws. In some cases they appeared to be even sunk beneath the 

 skin, and Mr. Trelease records the fact in a later letter that he has 

 seen the skin shed without the egg being also cast off. The adult flies, 



