STATE AGRICULTURAL 30CIET7. 
789 
TOBACCO-WORK. PARASITE DESCRIBED. ITS HEAD. ITS BODT. 
the worm, yet so slightly that they are liable to be detached by the slight¬ 
est force, some of them falling off, sometimes, merely from the motions of 
the worm. 
When these parasites issue from it the worm has become so weakened 
and exhausted that it ceases feeding and moving about, and in about three 
days afterwards all traces of its vitality have vanished. The multitude of 
minute hooks with which the soles of its pro-legs are furnished, however, 
continue to hold the dead worm to the stalk of the plant, with its head 
hanging downwards and its body shrunken and flaccid from the evapora¬ 
tion of its fluids, until some agitation of the plant by the winds or other 
violence detaches it and it falls to the ground. 
In the meantime the parasites change to puprn and after remaining in 
the cocoons seven days, they come out from them in their perfect form. The 
flies are black with clear transparent wings, and legs of a bright tawny 
yellow color, the hue of bees-wax, with the hind feet and the tips of the 
hind shanks dusky. They belong to the order Hvmenoftera and to that 
group of the Ichneumon-flies which in works of science have been termed 
Ichneumonid.es adsciti or the family Braconida:. Several of the species of 
this family present the singular character of having the eyes pubescent, 
numerous fine short erect hairs arising from their surface. These pertain 
to a particular genus which has received the name Microgaster, from two 
Greek words, equivalent to our English term “ small-bellied.” It is to this 
genus that these parasites of the Tobacco-worm belong. And they were 
described by Mr. Say, in a posthumous paper which was published in the 
year 1835, in the Boston Journal of Natural History, vol. i, p. 262, under 
the name Microgaster congregata or the Congregated Microgaster, in allu¬ 
sion to their young being found together in such numbers upon a single 
worm. 
The Tobacco-worm Parasite, Microgaster congregata, is of a coal black 
color and 0.14 long when living. After death it contracts in drying and is 
then scarcely 0.12 in length, and the male is a size smaller, not exceeding 
0.10. Its head is spheroidal, or of a flattened globular form, with the an¬ 
tennae inserted in the middle of the front side. The antennae are coarse, 
thread-like, and longer than the body in the male, shorter in the female. 
They are composed of about seventeen joints so closely connected that their 
articulations are diflicult to perceive. The joints gradually become slightly 
shorter and less thick as they approach the tips. The palpi and jaws are 
white. The eyes are distant from each other on the sides Of the head, and 
in a strong light their surface is seen to be closely bearded over with mi¬ 
nute short hairs. Between them on the crown the eyelets or ocelli appear 
as three small glassy dots placed at the corners of a triangle. The thorax 
is the broadest part of the body. It is egg-shaped, its surface minutely 
and closely punctured, and back of the middle it is crossed by a deep groove, 
fhc abdomen is oblong oval and about the same length as the thorax. It 
is smooth and shining, except the two first segments which arc rough from 
obscure shallow punctures, with an elevated longitudinal line in the middle. 
On its underside the three first segments are pale yellow, with a dusky 
