THE COTTON-WORM EGG-PARASITE. 193 



Let us now enter into a detailed account of these parasites. Up to 

 the time of the present writing thirteen distinct species parasitic upon 

 the cotton-worm, in one or another of its stage, have been bred in the 

 department. Of these, eight species are hymenopterous and five dipte- 

 rous. 



THE COTTON-WORM EGG-PARASITE (Tricliogramma pretiosa, Eiley). 

 In the latter part of the summer of 1878 a small lot of cotton-worm eggs 

 were received at the department, with which it was proposed to deter- 

 mine the time and manner of hatching, the length of time elapsing be- 

 tween the different moults of the worm, and various facts of that char- 

 acter. The eggs were placed in a glass breeding-jar, but much more 

 than the usual time seemed to elapse before the hatching. One morn- 

 ing, however, a number of very minute flies, so small as scarcely to be seen 

 with the naked eye, were found flying around the jar, and the eggs were 

 empty. Here, then, was a true egg-parasite, the mother fly having laid 

 her egg within the egg of the cotton-moth, and her progeny having lived 

 and undergone its transformations within that limited space. Whether 

 more than one parasite issued from a single egg was not determined. 

 These parasites belonged to the great hymenopterous family Clialcididae, 

 a family composed of a very great number of parasitic species, distin- 

 guished by their generally very minute size, brilliant metallic, or varie- 

 gated colors, elbowed antennae, nearly veinless wings, and naked pupae. 

 They are parasitic upon other insects in their early states j some, from 

 their minute size, are reared within the eggs of other insects, but the 

 majority infest larvae and pupae. They especially attack Lepidoptera, 

 but also attack species of some of the other orders. 



The species under consideration is one of remarkable beauty. The 

 general color is yellow, with brilliant red eyes. The wings are very del- 

 icate and transparent and present prismatic colors when viewed in dif- 

 ferent lights. The wings are fringed with excessively fine hairs j their 

 surface is also covered with still finer hairs. In length they are only a 

 trifle more than one-hundredth of an inch (.3 mm ), but, like all of the 

 subfamily to which they belong, are very 

 active and are great leapers, springing 

 sometimes to a distance of two or three 

 inches. 



An allied species (Trichogramma mi- 

 nuta) has been reared from the eggs of 

 the dissippus butterfly (Limenitis dissip- 

 puSj Godt.). In this case from four to six 

 individuals have been reared from a single FlG - 39.-Trichogramma miunta. 

 egg of the butterfly, and this seems to be about the normal number. It is 

 probable, then, that more than one parasitic egg is laid within the egg of 

 the cotton-moth. Fig. 39 (T. minuta, Eiley) will give a very good idea of 

 the general appearance of the magnified insect. The cotton- worm egg- 

 13 c i 



