158 HICKORY. LIMBS — HICKORY-GALL APHIS. 



are die excrement of a larva which lives in the walls of the gall, 

 mining cylindrical channels in it. This larva is about the tenth 

 of an inch long, shining watery whitish, with a pale yellow cloud 

 in the middle of its body, from visceral matter in the intestines, 

 and a flattened polished pale tawny head with the jaws appearing 

 like two brown dots on its anterior edge. It has no feet, and to 

 crawl forward it elongates itself and with its jaws grasps the 

 spongy side of its burrow, and then contracting, it draws its body 

 up towards its head. By this singular mode of progression it 

 moves along with rapidity in its burrow, but when placed upon 

 paper it strives in vain to lay hold of the smooth surface with its 

 jaws, and is incapable of advancing. It is quite probable that 

 this worm is the larva of the Elegant weevil above spoken of. 



It would be supposed that the lice which occupy these galls, 

 being wholly shut in as they are by a thick wall upon every side, 

 would be secure from the assaults of the numerous and inveterate 

 enemies of the aphides which have been noticed in the preceding 

 pages. But in one instance, four worms, which from their appear- 

 ance and motions I supposed to be the larvae of a Syrphus-fly, 

 were met with in one of these galls. They were the tenth of an 

 inch long, of an elongated oval form, more pointed anteriorly, 

 and of a pale rose-red color, with a broad yellow stripe in the mid- 

 dle from inclosed visceral matter. 



Though I have not been able to find winged individuals of 

 the insect which forms the galls upon the hickory twigs, it is so 

 like the Pemphigus bursarius of Europe in its habits, a species 

 which forms similar galls upon the leaf-stalks of the poplar, that 

 I entertain no doubt our insect is co-generic with that species. 

 We have still another species which is closely related to these in 

 its habits. It is the grape leaf louse {Pemphigus Vitifolice) of my 

 manuscripts, and forms small globular galls about the size of a 

 pea, upon the margin of the leaves of the grapevine. They are 

 of a red or pale yellow color, and their surface is somewhat 

 uneven and woolly. They are met with the fore part ot June, hav- 

 ing only the wingless females inclosed within them at that time. 

 These closely resemble the same sex in the species under con- 

 sideration. 



