THE AMERICAN ENTOMOLOGIST. 



JOl 



according to Mr. Trouvelot, deposits from eight 

 to ten eggs upon the skin of her victim, and the 

 young larvie soon hatch from tliem and com- 

 mence to prey upon the fatty parts of the worm. 

 But as only one of the parasitic hirvie can tind 

 food sutflcient to mature, the rest all die from 

 hunger, or else are devoured by tlie strongest 

 one which survives them. At first one would 

 8Ul)pbse that this deposition of several eggs by 

 the parent Ichneumon, where only a single 

 larva can develop, is a striking instance of mis- 

 directed instinct; but we tind a similar i)rodi- 

 gality throughout Nature, for every individual 

 is 80 subject to disasters of one kind or another 

 in its struggle for existence, that a provision of 

 several ova is often necessary to insure the 

 future development of a single one, just as we 

 often sow several seeds of some particular plant. 

 in order to insure the growth of a single one. 



After the Cecropia worm has formed its co- 

 coon, the parasitic larva, which had hitherto 

 fed on the fatty portions of its victim, now 

 attacks the vital parts, and when nothing but 

 the empty skin of the worm is left, spins its 

 owu cocoon, which is oblong-oval, dark brown 

 inclining to bronze, and spun so closely and 

 compactly, that the inner layers when separated 

 have the appearance of gold-beater's skin. If 

 we cut open one of these cocoons soon after it 

 is completed, we shall find inside a larfee fat 

 legless grub (Fig. 64), which sometimes under- 



[Pig. 64.] 



Color— Yellow c-i.. 



goes its transformations and issues as a fly in 

 the fall, but more generally wails till the fol- 

 lowing spring. 



TuE Cecuoi'ia Tachina Fly. — The Ichneu- 

 mon fly last mentioned usually causes a dwarfed 

 appearance of the worm which it infests, and 

 parasitized cocoons can generally be distin- 

 guished from healthy ones by their smaller 

 size. The larvie of the Tachina fly, which we 

 now introduce to our readers, as parasitic on 

 the ("ecropia worm, seem to produce an exactly 

 opposite eflecl — namely, an undue and unna- 

 tural growth of their victim. In the beginning 

 of September, 186G, we received from llocktord, 

 Ills., an enormous Cecropia worm. It measured 

 over four inches, was a full inch in diameter, 

 and weighed nearly two ounces; but like many 

 other large specimens which we have siuce seen, 



it was covered with small oval opaque white 

 egg-shells, clnsters of four or five occurring on 

 the back of each segment, invariably deposited 

 in a transverse direction. The skin of the 

 worm was black where the young parasites 

 had hatched and penetrated. This large worm 

 soon died and rotted, and in about twelve days 

 a host of maggots gnawed their way through 

 the putrid skin. Tliese maggots averaged about 

 one-half inch in length, and in torm were like 

 those of the common Blow-fly. The head was 

 attenuated and retractile and furnished with 

 two minute curved hooks, and the last segment 

 was squarely cut ott", slightly concave and with 

 the usual two spiracles or breathing-holes which 

 this class of larvae have at their tails. Their 

 color was of a translucent yellow, and they 

 looked very much like little pieces of raw fat 

 beef. They went into the ground and remained 

 in the larva state all winter, contracted to pupa? 

 in the April following, and the flies commenced 

 to issue the last of 



[Fig. 65.] 



Colors— Gray and black . 



May. This fly is 

 the Exorista ce- 

 cropia of our MS., 

 or Cecroi)ia Tach- 

 ina Fly, but as it 

 difl'ers, from the 

 Red-tailed Tach- 

 ina Fly (Uxorisia 

 milUaris, Walsh, 

 Fig. 65), which 

 similarly infests 



the Army-worm, in no other respect than y 

 in either lacking the red tail entirely, or in 

 having only the faintest trace oi it; and as 

 in a lot of the militaris bred last summer 

 from Army- worms, we find considerable dif- 

 ference in this respect, we prefer, rather than 

 multiply species on such mutable grounds, to 

 consider it as a variety of that species. We 

 infer that this same Tachina fly attacks the 

 Cecropia worm in widely different parts of the 

 couutry ; for we have this winter received from 

 Mrs. Mary Treat, of New Jersey, two diiiterons 

 pupte which probably belong to this species, 

 and which had also in the larva state infested 

 a Cecropia worm. 



The Cecropia Chalcis Fly— (Chalets maria, 

 N. Sp.*)— In May, 1869, we received from Mr. 



'Chalcis maria, N. Sp. — ? yellow, beautifully marked 

 with black. Head, yellow witli au arcuate black mark 

 behind base of the antenuK, corinected with a line short lon- 

 gitudinal black line leading to lower ncLlhis, aud from 

 thence to postei-ior margin of ociipul which is margined 

 with black; nrothorax with a medium black dot. Antenna 

 (scape '< H joints) 10-jpint«d; scape fulvous with superim- 

 edge black, flagellmn dark brown or black. TImrax with 

 large shallow close-set punctures: mesothora.x somewhat 

 striated trunsvcrbtly, triliuear with black, the three lines 



