OF THE STATE ENTOMOLOGIST. 87 



Northern Spy, Maiden's Blush, Benona, Soulard, Willow Twig, Lowell, 

 and Limber Twig as most free — his observations being made prin- 

 cipally in the orchard of J. W. Robson, of Galena, Ills., where the 

 trees alternated and were similarly situated with respect to outside 

 agencies. 



I once witnessed a very beautiful and striking illustration of this 

 truth in an orchard belonging to Mr. A. M. Herrington, of Geneva, 111. 

 Though, as already stated, the scales are found upon the wild Crab, 

 they are always so found in sparse numbers, which indicates that 

 the wild apple is not so congenial to the species as many of the culti- 

 vated kinds. Mr. Herrington has an orchard of about a hundred Ohio 

 apple trees, grafted on to crab stock, together with a few of the un- 

 grafted crabs. Scales are found on the grafted parts of almost all the 

 trees, but scarcely one can be found on the crab stock ; and in a few 

 instances the grafts are covered right down to the junction with the 

 stock, but do not go beyond. 



ENEMIES AND PARASITES. 



Besides mites* and lady-birds, the latter of which make ragged 

 holes through the scales, it has long been known that a little Hymen- 

 opterous parasite preyed upon this bark-louse, and in 1854 Dr. Fitch 

 was familiar with its larva, and figured a scale that had been perforated 

 by the mature fly.f It was not till the year 1870, however, that this 

 fly was really known and described by Dr. LeBaron, who has given 

 such excellent accounts of it,;]: that I prefer to quote his experience 



* These mites may generally be distinguished from the young bark-louse by having eighr legs in- 

 stead of six, tliougli some of them have but six legs in the larva state, and tliis criterion will not 

 always hold. Moreover, in the 8-legged species the front pair are easily mistaken for antennie. We 

 must therefore look for other distinguishing traits, and we And them in the relative position of the legs, 

 the third pair in the mites always being widely separated from the two front pair, while in the bark- 

 lice they are all equidistant. The mites are also more transparent and polished than the lice. There 

 are doubtless several mites which destroy the lice, and while one of the 8-legged forms has been de- 

 [Fig. 33.] ' scribed as Acarus'? mains by Dr. Shimer, he has proposed the name 



f/ of A. Walshii (Trans. Ills. Hort. Soc. 1869, p. 281) lor the 6-legged 

 y-^H^^^ form, but w'ithout description ; and indeed descri])tions, unless 

 /^^^:~Zf^ accompanied with habits, development and variation, amount, in 

 / Jr/f^xT" tbese cases, to very little. 

 > / I present, herewith, (Pig. 33), a side and ventral view of the 



/ species which so effectually destroyed the contents of the Georgian 



I { scales, in order that the reader may get a correct notion of the ap- 



/ y4ij, pearance of these mites. It may be a form of the .4c(r?-MS? ?;ifl/M.s of 

 A '" V>C^ Shinier, but differs from his desci'iption in being almost four times, 

 \ ^^ instead of twice, as long as broad, as well as in other details. The 



X J head and the limbs are yellowish, and more horny than the rest of 



/S-]\ the body, which is white. Four prominent hairs are seen from be- 



/ hind; and when the animal is crawling, a dorsal view discerns but 



' six legs, the posterior pair being smallest and apparently of little 



use, as they are generally curled up, as in the figure (a). The ends of the legs are flexile, and are 

 spread out in the form of discs in the act of walking. It apparently belongs to the genus Derma 

 leichus. 



tN. Y. Rep. I., p. 3.1. 



X Am. Ent. II, pp. .360-2: 1st Ills. Ent. Rep. pp. 34-9. 



