120 FIRST ANNUAL REPORT OF 



round the butt of the trunk, and even on the trunk and limbs, espe- 

 cially in places where a branch has been formerly amputated, and 

 nature is closing up the old wound by a circle of new bark. Where it 

 works upon the naked trunk, it often causes a mass of little granula- 

 tions to sprout out, about the size of cabbage-seeds, thus producing 

 on a small scale, the same effects that it does upon the roots. Wher- 

 ever the insect works, small as it is, it may be easily recognized by 

 the peculiar bluish-white cottony matter which it secretes from its 

 bod3 r , and which is never met with in the case of the common Apple- 

 tree Plant-louse that inhabits the leaves and the tips of the twigs. 



Figure 04 at the head of this article, fully illustrates the Apple- 

 root Plant-louse. A portion of a knotty root as it appears after the 

 punctures of the lice is represented at a, the larva state at b, and the 

 winged state at c\ while ^represents the leg, e the proboscis, f the 

 antenna of the winged individual, and g that of the larva, all highly 

 magnified. The young louse is of a deep flesh or pink color, and the 

 proboscis extends the whole length of the body, while the older spe- 

 cimens have a deeper, purplish hue. Of the winged louse, I subjoin 

 a more complete description. 



Eriosoma pyri, Fitch — Color black. Antenna? 2-5ths as long as the body, joints 1 and 2 al- 

 most confluent, short and robust; joint 3 fully \ the entire length of the antenune : joints 4 — 6 sub- 

 equal, 5 a little the longest, 6 a little the shortest. Meso-thorax polished. Abdomen opaque with 

 more or less pruinescence. Legs opaque black, immaculate. Wings hyaline ; costal and subcostal 

 veins robust and black ; stigma pale brown, 2} to 3 times as long as wide, pointed at both ends, but 

 more acutely so on the basal end, the vein bounding it behind robust and black. Discoidal veins 

 and stigmal vein slender and black, the 3d or forked discoidal hyaline and subobsolete on its basal J. 

 Length to tip of closed wings 0.13 — 0.14 inch. 



On comparing Figure 64 c with Figure 65, which represents a 

 [ Fi &- 65 -l Plant-louse that inhabits a large gall 



H on the Cottonwood, it will be observed 

 I at once that the veining of the front 

 wing is very different. In Figure 64, c, 

 the third branch-vein is very distinctly 

 1 — I — ' forked ; in Figure 65 it is simple. Nor 



is this a mere accidental variation, but a peculiarity of the genus to 

 which either insect belongs. (Fig. 64, c, genus Eriosoma ; Fig. 65, 

 genus Pemphigus). Now Dr. Fitch describes and names the Apple- 

 root Plant-louse as belonging to the latter genus {Pemphigus) ; where- 

 as winged specimens which both Mr. Walsh and myself obtained last 

 October, at Duquoin, from apple roots and suckers swarming with 

 larvae ; some which I received lrom St. Louis county, and others which 

 Mr. Walsh bred from larvae ; all, without exception, ^belong to the 

 former genus (Eriosoma). And moreover, Dr. Fitch's insect is de- 

 scribed 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 but two in number, and they were found by 

 him, the one living, the other dead, upon the roots of an infested 

 young apple-tree, which had been brought him from an adjoining 

 county. Hence he very naturally, but as we think erroneously, infer- 



