558 
HYMEN OP TER A. 
to me the result of his interesting observations. lie lias 
come to the conclusion that the joint-worm is the larva of a 
Hymenopterous, and not of a Dipterous insect. He finds 
that the parts of its mouth are very different from those 
of the dormant larva of the Hessian fly (the latter ex- 
tracted from its flax-seed case before it had undergone any 
change of form), and that the mouth of the former agrees 
essentially with that of the larvae obtained from galls of 
the oak. In the mouth of the joint-worm he observed that 
“ the mandibular hooks cross each other on the middle line,” 
while in the Hessian fly larva the “ two hooks are directed 
downwards.” His samples of diseased wheat-straw of the 
previous year yielded him, in the spring, numerous speci- 
mens of the Eurytoma , and nothing else. A few specimens 
of the same insect were developed from the tumors on 
plants of the present season, thus showing that “ a small 
proportion of the larvae undergo their transformations during 
the summer.” Among his specimens he obtained a very 
few Hymenopterous insects, differing from the Eurytoma , 
and probably parasites. In several instances Professor 
Cabell saw a small semitransparent whitish worm, scantily 
covered with hairs, in the same cell with a lifeless joint- 
worm, and adhering to its body. In other cases, the former 
kind of worm or larva “ was found alone, but it was then 
of a larger size, and there were almost always some more 
or less unequivocal signs of the worm having fed on the 
joint-worm.” 
Having been favored by Professor Cabell with some sam- 
ples of wheat-straw, containing living joint-worms, I have 
been able to verify his observations during the present sum- 
mer, while this sheet is passing through the press. At my 
request, Professor Jeffries Wyman, of Harvard College, an 
accomplished anatomist and a skilful microscopical observer, 
has examined these larvie, and also some of the parasitical 
worms, found in the straw, and has made for me several 
magnified sketches of them. Both kinds are found to differ 
O 
