OF THE STATE ENTOMOLOGIST. 93. 



other course could well have been taken, considering our imperfect 

 knowledge of them in the past ; but it is evidently a very artificial one. 

 We now know that some of the larger species thrive on plants of 

 widely different families, and a correct knowledge of the present rela- 

 tions of these bark-lice will first be had, when, by prolonged experi- 

 ence and deeper search, we understand all the more minute structural 

 differences; the variation resulting from phytophagism or cause what- 

 soever, and the male as well as female characters. 



It has generally been supposed that our Oyster-shell Bark-louse 

 is the same species originally mentioned by Keaumur, in 1738, (Mem. 

 Tom., IV, p. 60), and found in Europe on the Elm. Doubts have existed 

 as to the identity of the two, because of the difference of food-plant; 

 but his account and description of the insect itself agree otherwise 

 with ours. In 1762 Geoffroy described a species supposed to be the 

 same, by the name of arhorum-lineains^ and twenty-six years after- 

 ward Gmelin gave the name concliifonnis to what has also been con- 

 sidered the same insect. Geoffroy's name has been very generally 

 ignored, because of its non-conformity to existing rules of scientific 

 nomenclature, and of the inappropriateness of the term, if intended 

 for our apple-tree species. In 1851 Bouche (Stett. Ent. Zeitung xii. 

 No, 1) gave to a similar species, occurring on the Apple in Europe, the 

 name of pomorum^ which has either been considered synonymous 

 with the others, or entirely ignored by most subsequent authors. 

 Signoret; in the second part of the essay already referred to, consid- 

 ered all these names synonymous ; but he subsequently changed his 

 mind, and in the sixth part of his essay he has employed each of the 

 three names for what he considers distinct species, and has charac- 

 terized them as follows : 



M. linearis (Geoff.) is found on the Linden, and is supposed to differ from Qonchi- 

 fortnis by the shield being long, more or less sti-aight, of a yellowish-brown color, and 

 generally covered with a soot-like snbstance ; by the female being nearly as broad be- 

 fore as behind, and by the secretors on the anal plate being nearly continuous, the 

 middle set witli 6 or 7, the upper laterals with 10 or 12, and the lower laterals with 9 or 

 10. The i^* is unknown. 



31. co7ichiformis (Gmelin) is the species found on Elm, and which differs in no 

 respect from the apple species, except in the number of anal secretors possessed by the 

 female, the median set composed of 6 or 7, tlie upper laterals of 8 or 9, and the lower 

 laterals of 5 or 6. Signoret says that the male scale is of a pale yellow, and with straight 

 and parallel sides, while the male is described, from a mutilated specimen, as pale gray, 

 with the antennae appearing short. 



M. pomorum (Bouche) is the species found on Apple, and it differs from the pre- 

 ceding, principally in the median set of secretors in the female being composed of 17, 

 the upper laterals of 17, and the lower laterals . of 14. Tiie eggs are described by 

 Signoret as being of a deep red, and the antennae of the active larva as 6-jointed. The 

 scale has the same form, but is described as brownish-black, with a portion of the 

 " apical border white and more oblong." Bouche, in characteristic German, describes 

 it as ham-muscle-shaped (schinkenmuschelformig), slightly bent, and with the pointed 

 end, and edge of broad end, yellowish. He also describes the eggs as red browyi, and 

 mentions the food-plants as "Apple, Pear, Plum, Dogwood, etc." 



