ACTING STATE ENTOMOLOGIST. 
41 
shell Bark-louse, never acquires any wings at all, and which loses even its legs when 
it is only a few days old, and becomes as stationary as a cabbage for the remaining 
period of its existence, can pass from tree to tree in the manner that we know it to do. 
Dr. Fitch, indeed, talks very glibly and fluently about the Bark-lice on some trees, 
that w'ere “perishing” with their enormous numbers in the month of September, 
“preferring starvation at home” to being “poisoned by invading” some neighboring 
trees that had been dosed with one of the thousand-and-one Anti-Bark-louse Specifics. 
(N. Y. Rep. I., p. 38.) He might as well talk about the apple trees, in a badly-cultivated 
orchard, “ preferring starvation at home” to emigrating into some well-kept and 
well-tended orchard. For, in September and, indeed, during the entire year, with the 
exception of three or four days in the spring, the female Bark-louse is as incapable 
of emigrating as an apple tree 5 and, as to the males, they, of course, could do no haim 
to a tree, even if they covered its entire surface ; for, like all male insects belonging 
to this family, they have no beaks or mouths of any kind, and of course they lay no 
eggs. In my opinion, the only way in which, as a general rule, Bark-lice can spread 
from tree to tree, w r lien the boughs of those trees do not interlock, is by a few of the 
very young larvae, when they are first hatched, and are scattered over the limbs oi 
a tree in such prodigious numbers, crawling accidentally on to the legs of some bird, 
that chances to light upon that tree and afterwards flies off to another. I have long 
observed that, when a tree first begins to be attacked by Bark-lice, it is only particular 
limbs and branches that are at first infected, and that these will be swarming while the 
rest of the tree will be free from lice. And I have further observed, that it is the lower 
horizontal limbs and branches, or such as birds, with the exception of Woodpeckers 
and Nut-hatches, would most naturally perch on, that are first attacked. The process 
of transmission, however, is by no means so sure and speedy as in the case of "winged 
insects —for example, the Plant-lice (Aphis family.) For every one must have often 
noticed trees standing not far from one another, some of which were swarming with 
Bark-lice while others were not in the least infected. If all the birds in the world were 
killed off, I believe that these Bark-lice, in a very few years, would cease to exist. 
They would first of all destroy the trees of which they had already got possession ; 
and then they would all of them die of starvation themselves. As to the popular idea 
that all Bark-lice crawl along the ground from one tree to another, that is altogether 
out of the question. They only possess the power of crawling for a few days, and they 
crawl so exceedingly slow, that I do not believe that in that whole time they could 
make more than a few yards, even on a perfectly smooth surface. Is it likely, then, 
that they can ever crawl down the trunk of their own tree, make theii way over many 
yards of ground which is always more or less rough, and then crawl up the trunk 
of another tree and pass along on to its branches ? 
Mites (Acarus family) are not time Insects, but belong to the same Class ( Arachnida ) 
as the Spiders and the true Ticks as distinguished from the so-called Slieep-tick, which 
is a wingless true Insect and — if the hibernicism may be pardoned a wingless Two¬ 
winged Fly (Order Diptera). In common with the rest of the Class to which they 
appertain, Mites differ essentially from all the true Insects in having the head and thorax 
all in one piece, without any free joint or even any suture between them. They diffei 
further, almost all of them, in having eight legs in the perfect state ; whereas all true 
Insects without a single exception have in the perfect state exactly six legs, never moie 
and never less. In very many genera of Mites, howe^ er, as in certain genera of Insects, 
the first pair of legs are not used in walking, but are constantly vibrated up and down 
