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powers, the base of the median being quite disconnected from the 
submedian. In one of my specimens there was no vein extending 
from the subcostal knob to the end of the wing. 
The legs are pale straw-yellow, the fore shank-joints (tibiae) and 
toe-joints (tarsi) brownish; the third hip-joints (femora) are dusky 
on the basal half, while the hind terminal tarsal joints are brown. 
The abdomen is small, black', while the head and thorax are bright 
metallic green, sometimes blue. The abdomen is also smooth and 
polished, much flattened, oval, not so wide as the thorax, broad at 
the end and suddenly pointed (mucronate) at the tip. It has a 
large yellowish patch on the upper and under side of the second 
segment. Length of the body 2-2% millimeters (.08-. 11 inch). 
The female differs in her greater size and rather slenderer body, 
and the more club-shaped antennae, the terminal joint being twice 
as long as thick. The abdomen is as long and as wide as the 
thorax, ending in a long sharp point, the short but distinct ovi¬ 
positor extending slightly beyond the tip of the body. There is a 
slightly marked pale spot above on the second segment. Length 
2%-3 millimeters (.10-. 12 inch). 
This parasite was first described by Say, his specimens occurring 
at or near Philadelphia; it was observed by Herrick in 1833, in 
Connecticut, and in 1877 we bred it from puparia of the Hessian- 
fly received from Ohio; and, as stated by Professor Cook, it is 
sufficiently abundant in Michigan to destroy the Hessian-fly in 
great numbers, and is probably distributed throughout the Hessian 
Fly area. 
So destructive is this and other parasites to the Hessian-fly that 
as early as 1841 Herrick claimed that in Connecticut “a very largo 
proportion, probably more than nine-tenths , of every generation of - 
the Hessian-fly is destroyed by parasites.” This work is mainly, 
we doubt not, done by the chalcid parasite under consideration. It 
is to this insect more than to any other means in nature that we 
owe the general immunity in certain years from the attacks of the 
Hessian-fly in most wheat regions, and to this cause that during 
certain years the fly is kept wholly within bounds. Few people, 
even naturalists, have any adequate idea of the good done by these 
minute parasites. What was the fact in Connecticut, in 1841, and 
the few years preceding, has been the case ki Michigan, according 
to Mr. F. S. Sleeper, of Galesburg, Mich., who writes us that the 
Hessian-fly was nearly exterminated in Kalamazoo county by 
Semiotellus destructor , nearly all the “flaxseeds” in the crop of 1877 
having been destroyed by this friendly parasite. He writes us that 
in the autumn of 1877 he found these parasites in the wheat-fields 
in countless numbers, and that the perfect Hessian-fly was difficult 
to find. 
No one, since Herrick recorded his observations, has made very 
careful observations on the habits of these parasites. He states 
that: 
“It pierces the sheath of the stalk (making a hole too small to be 
detected by a powerful microscope), and deposits an egg in the pupa 
within. This is chiefly done in June. The perfect insect is evolved in 
the summer and autumn succeeding, eating its way through the 
puparium and the sheath of the leaf.” 
