82 



THE AMEEICAN ENTOMOLOGIST. 



two other such, species that infest respectively 

 the Hickory and the Oak. Whether any or all 

 of these species likewise infest the roots of the 

 trees upon which the)' occur, remains to be 

 ascertained. Bnt certainly they can never emi- 

 grate on to the Apple; for the Apple, the Elm, 

 the Ash, the Dogwood, the Hickory, and the 

 Oak, all belong to different botanical families ; 

 and no Plant-louse that lives upon a plant be- 

 longing to one botanical familv, can live when 

 transfen-ed to a plant that belongs to a different 

 botanical family. Even when two plants belong- 

 to different geitera of the same botanical family, 

 it is not often that the same Plant-louse will live 

 indifferently upon either; and frequently the 

 same Plant-louse will not even live indifferently 

 upon two plants that belong to the very same 

 botanical genus. "We have a remarkable exam- 

 ple of this last fact in the common Currant 

 Plant-louse, which swarms in almost every gar- 

 den upon the Currant, and yet was never known 

 to shift its quarters on to the Gooseborrj' — a 

 species that belongs to the very same genus 

 (Sibes) as the Currant. Indeed so far is this 

 from being the case, that nobody ever saw 

 Plant-lice of anj^ kind whatever infesting the 

 Gooseberry. 



[Fig. 70.] 



Colors— (6) diill lead color; (c) black. 



Fig. 70, 6, shows the Apple-root Plant-louse in 

 the larva state, with the usual Avooly matter 

 attached to its back. Fig. 70, c, shows the same 

 insect in the perfect or winged state, with the 

 wooly matter all removed.* On comparing 



» We annex the technical description of this Plant-louse, 

 drawn up from the recent specimen. 



The AppL35-itooT Plant-lodse (Eriosomrt pyri, Fitch.) 

 Black. AntenniE2-5ths aslong as thebody, joints 1 and 2 al- 

 most confluent, short and robust ; joint .3 fully J the entire 

 length of the antenna ; joints 4—0 snbequal, 5 a little the long- 

 est, 6 a little the shortest. (Fig. 70, /, that of the Winged- 

 louse; y, that of larva, both highly magnified.) Meso-thorax 

 polished. Abdomen opaque with more or less pruines- 

 cence. Legs (see Fig. 70, d) , oparjue black, imma- 

 culate. Wings hyaline; costal and subcostal veins robust 

 and black; stigma pale brown, 2J to 3 times as long as wide, 

 liointed at both ends, but more acutely so on Ihe basal end, 

 the vein bounding it behind robust and black. Discoidal 

 veins and stigmal vein slender and black, the 3d or forked 



this last with Fig. 71, which represents a Plant- 

 louse that inhabits a large gall on the Cotton- 

 wood, it will be observed at once that the vein- 



[Fig. 71.] 



Color— Black. 



iugof the front wing is very different. In Fig. 70, 

 c, the third branch-vein is very distinctly forked ; 

 in Fig. 71 it is simple. Nor is this a mere acci- 

 dental variation, but a peculiarity of the genus 

 to which either insect belongs. (Fig. 70, c, genus 

 JEriosoma ; Fig. 71, genus Pemphigus) . Now Dr. 

 Fitch describes and names the Apple-root Plant- 

 louse as belonging to the latter genus {Pemphi- 

 gus) ; whereas out of 10 winged specimens ob- 

 tained by ourselves at Duquoiu, S. 111., in the 

 middle of October, 18C8, upon apple roots and 

 suckers swarming with larvse, and 3 other 

 winged specimens actually bred October 21 and 

 22 from larvte obtained from Dr. Weed, Musca- 

 tine, Iowa, all without exception belong to the 

 former genus {JEriosoma) . And moreover. Dr. 

 Fitch's insect is described as being nearly twice 

 as large as ours. How does this come about? 

 We can only account for it in the following way : 

 Dr. Fitch's winged specimens were bnt two in 

 number, and they were found by him, the one 

 living the other dead, upon the roots of an in- 

 fested youn^- apple-tree, which had been brought 

 him from an adjoining county. Hence he very 

 naturally, but as we think erroneously, inferred 

 that these two winged Plant-lice belonged to the 

 same species as the minute wingless larvte with 

 which the infested roots were swarming. The 

 truth of the matter probably was, that the two 

 winged plant-lice got ui)on the infested apple- 

 root by accident, on their road from the nursery 

 to Dr. Fitch's orchard. Indeed we can almost 

 say with certainty to what species they be- 

 longed; for on comparing Dr. Fitch's very 

 minute and elaborate desci-iption with the Beech- 

 twig Plant-louse {Pemphigus imbricator, Fitch) , 

 which comes out in the winged state in the very 

 same time of the year as he met with his two 

 specimens, it agrees sufficiently well to apply to 

 that species. If, on tlic other hand, we compare 



discoidal hyaline and subobsolete on its basal i. Length to 

 tip of closed wings 0.13—0.14 inch. 



Nine specimens, 3 recent ones from Iowa bred October 21- 

 22, 6 dried ones from S. Illinois, captured at Uuqnoin Octo- 

 ber 16. In one wing of a single specimen there are two stig- 

 mal veins, one inclosed by the other, and the inner one 

 springing from near the tip of the stigma . No apparent vari- 

 tion whatever inthc structure of the 3d or forked discoidal 

 iu any of the IS wings. 



