THE STATE ENTOMOLOGIST. 15 



two last scales are constructed by the louse, of its own cast skins and 

 some excrementitious secretion, as he suggests, is also made ex- 

 tremely doubtful, from the simple fact that you may raise them every 

 day of their growth and find the louse underneath, entirely free and 

 separate. But after all, though of great scientific interest this matter is 

 of no practical importance whatever, for as we shall see hereafter 

 the great point to be borne in mind, in a practical light, is the time 

 of hatching of the egg. 



As the female Bark-louse is only capable of motion for a period 

 of from two to three days at the most, after which time she becomes 

 as permanently fixed for the rest of her life as is the tree on which she 

 is fastened ; and as the winged males (even if they ever exist) could 

 not assist in the spread of the species, it may puzzle some to divine 

 how this insect spreads from tree to tree and place to place. That it 

 is transported to distant places, mainly on young trees, there can be 

 no doubt, and there are various ways in which it can spread from 

 tree to tree in the same orchard, though it can only thus spread dur- 

 ing the few days of its active larval state. Mr. Walsh believes that 

 the only way, as a general rule, that it can spread from tree to tree, 

 when the boughs of those trees do not absolutely interlock, is by a 

 few of these active young larvee, crawling accidentally on to the legs 

 of some bird, that chances to light on one tree and afterwards flies to 

 another, and he even goes so far as to say that he believes this Bark- 

 louse would soon cease to exist, if all the birds in the world were 

 killed off (Jtep. p. 41). My friend Walsh seems to have a special 

 grudge against the birds, and it is hard to imagine how he could make 

 such a statement, in face of the fact that where there is one bird, 

 there are a hundred insects roaming constantly from tree to tree, that 

 are just as capable of giving the young lice a lift. Moreover the 

 specific gravity of the young louse is so slight that it almost floats in 

 the air, and is undoubtedly aided in spreading by the winds ; while on 

 a tree very thickly covered with old scales, its traveling propensities 

 are sufficiently developed to cause it to run down the trunk of the 

 tree and even over the ground, and as it travels at the rate of two or 

 three inches per minute, it could manage to measure several rods with 

 its microscopic legs, in the course of its active state. 



Though essentially belonging to the apple tree, this Muscle- 

 shaped bark-louse is not unfrequently found both upon the Currant, 

 the Plum and the Pear. I have seen the scales fully developed and 

 bearing healthy eggs on the fruit of the White Doyenne pear, of the 

 Transcendent crab, and of the wild j)\um (Prumis Americana) which 

 have been sent to me by Mr. T. D. Plumb, of the State Journal, Madi- 

 son, Wisconsin; and, though on the hard bark of a tree, we cannot 

 judge of the amount of sap they absorb, it is quite apparent on these 

 soft fruits, for each scale causes a considerable depression from the 

 general surface. I have also received twigs of the Persian lilac from 



