52 



Hitherto we have spoken only of the mother Bark-louse. I have 

 not actually bred the males of the Oyster-shell species; but there is 

 good reason to believe that a small percentage of the larvge — consid- 

 erably less than five per cent, on a rough estimate — which never, like 

 the egg-bearing females, have any long "anal sack'" grow out of their 

 tails, subsequently develop into males, and again acquire the power 

 of locomotion. Even in the winter time, the empty shells of these 

 individuals may be seen still adhering to the bark. Throughout the 

 Bark-louse Family, it is the males only that ever acquire any wings, 

 or even any rudiments of wings; and in comparison with the females 

 of this species, the males, judging from the minute size of the scales 

 out of which they, in all probability, come, must be very small and 

 insignificant fellows indeed. The same law obtains throughout the 

 whole Family. 



It is a curious question how a species of insect, which, like the 

 female of this Oyster-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 were "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 Spe- 

 cifics. {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 ex- 

 ception of three or four days in the spring, the female Bark-louse is as 

 incapable of emigrating as an apple tree; and, as to the males, they, 

 of course, could do no harm 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, when the boughs of those trees do not inter- 

 lock, is by a few of the very young larvae, when they are first hatched, 

 and are scattered over the limbs of a tree in such prodigious numbers, 

 crawliug accidentally on to the legs of some bird, that chances to light 

 upon that tree and afterwards flies off to another. I have long ob- 

 served 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 



