20 
The infested chrysalids of the butterfly may usually be, distinguished 
by the livid and otherwise discolored and diseased appearance of the 
body. 
I do not know that these parasites select any particular point of 
the chrysalis shell at which to make their escape, but in those I have 
observed, the place of exit appears to have been generally at or near 
the point where the abdomen joins the thorax. 
F 4 In Europe*there is a small Chalcid species— Microgaster 
glomeratus , Linn., which attacks the caterpillar, deposit- 
" ing thirty or more eggs in its body, the maggots hatch 
from these, feed internally upon the worm, weakening it 
but not destroying its life until they are ready to trans¬ 
form into pupae—then it dies, and they, yet in the larval 
\ state, make their way through the skin and spin little 
Microgaster elongate-oval silken cocoons, in masses, beneath and 
militaris. around it. 
Although this species, so far as I am aware, has not yet been ob¬ 
served infesting these cabbage-worms in this country, yet cocoons 
somewhat similar to those made by it have been found about the 
caterpillars of P. rapce. I insert here a description of it, copied from 
Curtis: 
“It is black and thickly punctured; the horns are thread-like, longer 
than the body in the male, shorter in the females, and composed of 
eighteen joints or upwards; the eyes are lateral, with three, little eyes 
or ocelli upon the crown; the abdomen is shorter than the thorax, de¬ 
pressed, linear, smooth and shining; the basal segment is a little nar¬ 
rowed, with the edges on the sides dirty white; ovipostor concealed 
beneath the abdomen; the four wings are very transparent, iridescent, 
with a distinct pitchy-colored stigma on the superior; the nervures 
lighter, the areolet open externally; legs bright ochreous, hinder-thighs 
black on the upper edge, darkest at the apex, tips of their shanks and 
tarsi brownish, the apex only of the four anterior brown; length a 
little more than one line; expanse 2f lines.” 
According to this author, the little cocoons are bright yellow. I 
have found this season, upon the cabbages where the worms had been 
at work, similar little cocoons, except that instead of being bright 
yellow, they are of a creamy white; but I have not yet seen the per¬ 
fect insect.* 
Mr. Provancher, of Quebec, was the first to call attention to an¬ 
other parasitic fly, which belongs to the same group as, and resem¬ 
bles, the common house-fly. This is a species of Tachina, and the 
maggot which resides in the body of the cabbage-worm, living on the 
fatty portions, is, according to Dr. Packard, flattened and sub-cylin¬ 
drical, with both ends of it rounded much alike; the mouth-parts 
partly aborted, there being only two retractile horny mandibles, by 
which the fatty portions of its host are eaten. 
There are other Ichneumon flies, which I am inclined to think are, 
at least occasionally parasitic upon the worm, as I have noticed them 
frequently about them and on the cabbages where the worms were at 
work. One, apparently a Microgaster, and another, supposed to be a 
Pimpla. Some fifty or sixty cabbages in my garden were devoted to 
♦Since this was written. Mrs. Thomas has succeeded in obtaining- the perfect insect, 
which appears to be identical with Microgaster militaris. (Fig.4) 
