794 
ANNUAL REPORT OF NEW YORK 
TOBACCO-WORM. PARASITE AND ITS DESTROYER. THEIR DIFFERENT MOTIONS. 
dinal vein is perceptible, which, near its middle, gives off a branch running 
almost to the inner hind end of the wing. The hind wings are much 
smaller and without veins, except a brown subcostal one, which extends 
into the outer margin and abruptly ends a little beyond the middle. 
All the examples of this species which I have obtained from cocoons upon 
the Tobacco-worm have been females. The last of August 18G2, I received 
from Dr. Allen of Saratoga Springs, a larva of the Sphinx Kalmice to which 
thirty-six cocoons were adhering. And the middle of July, the following 
year, H. Markham, Esq., of Stony Brook, Long Island, sent me the samo 
larva, similarly infested. It may here be incidentally observed that both 
these gentlemen met with these larvaj upon the leaves of the grape-vine. 
As I have repeatedly observed it, in different years, upon the lilac, the 
leaves of which arc certainly its usual food, the interesting query arises, 
whether, when it is infested internally with parasites, they do not cause a 
morbid appetite in the worm, whereby it ceases to relish its nat¬ 
ural food and comes to crave the leaves of the grape in place 
of those of the lilac 1 Plies were obtained from more than half the 
cocoons upon the first mentioned worm, and these being all of one 
species I supposed they were probably the true parasites of the Lilac-worm. 
But I now find on comparing them, that they are identical with this species 
which is now under consideration. It thus appears that the cocoons adher¬ 
ing to the Lilac-worm had been formed by a species of Microgaster, prob¬ 
ably this same species which infests the tobacco-worm, and that the flies 
I obtained were its parasites and consequently were protectors instead of 
destroyers of the Lilac-worm. The cocoons from Mr. Markham, might per¬ 
haps have given more light upon this subject, and I now regret that, when 
they came to hand, supposing they would only produce the same flies which 
I had examined the preceding summer, I felt that it would be a waste of 
time to attend to the rearing of their inmates. 
Of the flies obtained from the Lilac-worm, four were males, whereby it 
appeals that this sex differs from the females above described, in the fol¬ 
lowing particulars: 1st, their color is lighter and more bright, being 
brilliant metallic green, when dried becoming blue green; 2d, their antennm 
are tarnished yellow, longer, and not at all thickened toward the tips, 
their joints being cylindric and a third longer than thick, with the last 
joint egg-shaped and but little longer than its predecessor; 3d, the abdomen 
is flattened oval and rounding at its tip, with a large translucent pale yel¬ 
low spot near the base; 4th, the legs are paler and pure yellow without 
any mixture of orange or tawny. 
One who is acquainted with this insect and the Microgaster fly, will 
readily distinguish them by their motions, notwithstanding their smallness 
and similarity in size. The Microgaster is very brisk and active in its 
movements, running about with agility and flying away if any danger 
menaces it. this insect, on the other hand, appears tame and sedate, walk¬ 
ing around slowly, and as if with deliberation as to what it is doing; and 
if any annoyance approaches it, to escape therefrom it gives a slight skip, 
throwing itself about an inch, and repeating this leap again and again if 
pursued, it being not at all inclined to take wing. 
