16 WHITE-MAEKED TUSSOCK-MOTH. 



mon over the whole. Upon opening the cocoons, I found, with 

 very few exceptions, not pupae, but partly changed caterpillars, 

 dead and dry, and in each of these two or three, and sometinaes 

 four coarctate pup?e, of a regular oval form and mahogany color, 

 evidently belonging to some parasitic two-winged fly. In some 

 were found the larvae or maggots, not yet changed to pupte. 



They are from three to four-tenths of an inch in length, and present the ordinary 

 characters of the larvfe of the Muscidai or fly family. The body is somewhat tapering, 

 anteriorly, and capable of considerable extension. The only parts of the mouth visible 

 are two minute, curved, black mandibles or teeth. The body is rounded, posteriorly, 

 with a shallow depression, in which are situated two conspicuous spiracles or breathing 

 pores. On all the rings, but mostly on those nearest the extremities, are numerous mi- 

 croscopically minute, black, spinous points. These points extend all around the body, 

 beneath, as well as above, and probably assist the larvte in the slight locomotion which 

 it requires. The pupa is a quarter of an inch long, with slight, but distinct segmental 

 incisions, and even with vestiges of the spinous points of the larva, proving that the 

 covering or case of what are known as coarctate pupre is really only the skin of the 

 larva contracted and hardened. 



Tiie parasitic flies began to emerge from their pupal cases during the first week of 

 September, and proved to belong to the genus Tachina, proper, as restricted by Mac- 

 quart, and to section AAA, distinguished by having the third joint of the antenna a 

 little more than twice the length of the second. They resemble the common house-fly, 

 but are somewhat larger and have more bristly bodies. Many of the Tachbice bear a 

 close resemblance to each othet, and are therefore difficult to distinguish from each 

 other by merely verbal descriptions. This species maybe appropriately named the Tach- 

 ina orgyice. Length about one-third of an inch; sides of front, pale golden; middle 

 space, velvet black ; face, silver-ash; fascial bristles, reaching nearly to the middle of 

 the face ; eyes, bare ; third joint of antennae, a little more than twice as long as the sec- 

 ond; second joint of the seta, well developed; third joint of seta, thickened for half its 

 length; palpi, brownish; thorax, with alternate stripes of black and dusky cinereous. 

 First longitudinal vein of the wings, after the auxiliary, reaching the middle of the 

 costa. Third and fourth veins, almost meeting, some way before the tip of the wing. 

 Fourth vein, prolonged beyond the curve, half way to the border. Discal cross vein re- 

 moved its own length from the border, and more than half its length from the flexure 

 of the fourth vein. Abdomen black with cinereous reflections at the incisions and on 

 the basal half of the segments, except the first. Two bristles on the hind margin of 

 tlie first and second segments. Terminal segments many bristled. 



Of the myriads of cocoons here accumulated, it appeared tliat 

 scarcely one out of a hundred had escaped the fatal visitation of 

 those parasites. So that the race of caterpillars, so abundant and 

 destructive this year, may be considered as practically extermi- 

 nated in this locality. 



It might seem, at first sight, that a knowledge of parasitic in- 

 sects is of no practical importance, inasmuch as they carry on their 

 beneficent work wholly irrespective of our cognizance or co-ope- 



