ORDER VI.—VEIN-WINGED INSECTS. 243 
All the insects of this order thus far enumerated are 
more or less useful to man, by their agency in the destruc- 
tion of such a vast number of caterpillars, grubs, and other 
insects directly injurious to vegetation. But we must men- 
tion one family of the ichneumons that are as destructive to 
vegetation as they are to the caterpillars, viz., that com- 
posed of the several genera of the Saw-wasp. 
Now there is one fact in connection with the larve of this 
family which should be mentioned in the beginning. The 
true caterpillars, which are metamorphosed into moths and 
butterflies, never have more than sixteen legs; but many 
of these larvz are found which almost exactly resemble 
caterpillars in appearance, but which have more than eight 
pairs of legs, and these are called pseudo or false caterpil- 
lars, because *they do not transform into lepidoptera, but 
into hymenopterous insects. 
Formerly, many experienced naturalists held the opinion 
that all the wasps which they found issuing from the co- 
coons spun by these pseudo-caterpillars were the produc- 
tion of ichneumons; but more extensive and closer investi- 
gations proved this to be an error. ‘The pseudo-caterpillars 
proceed from eggs deposited by different species of hymen- 
optera, and each propagate their own species, some being 
ichneumons, others very different species of wasps. Those 
which feed on leaves deposit their eggs on them, while other 
wasps, which feed on wood, deposit their eggs under the bark 
of trees. When fully grown, most of the caterpillars go to the 
ground, and transform themselves into cocoons under its sur- 
face. None of these wasps are provided with a venomous sting. 
Notwithstanding the pseudo-caterpillars, like the true 
ones, are ornamented with a great variety of colors, cast 
their skin four times, and spin silky cocoons, yet they may 
be recognized as false by their globular brown or black 
head, and by the number of their feet, which sometimes is 
eighteen, sometimes twenty, and even twenty-two. 
