lOti TRANSACTIONS OF THE ILLINOIS 



The galls usually begin to appear early in May, and at first are occu- 

 pied by a single wingless female, which in midsummer becomes the mother 

 of a numerous progeny, often amounting to one hundred and fifty in 

 number. Dr. LeBaron is of the opinion, from some observations he 

 made, that they pass the winter in the egg state, and that the eggs are 

 placed at the base of the buds. 



The young lice are of a pale greenish or whitish color, variable in 

 size, but usually about three-hundredths of an inch long. The winged 

 individuals make their appearance about the middle of June. These are 

 of a blue-black color throughout, sometimes with the base of the abdo- 

 men and legs pale brown. While in the gall the wings appear to rest 

 horizontally on the back, but when they leave this they are held erect in 

 repose, as is usual with the species of this genus; they are whitish and 

 not perfectly clear, being more or less dusted over, as is the body, with a 

 white powder : the marginal vein is robust and blue-black from the base 

 to the stigma, but slender beyond that point; the rib-vein is also robust 

 and of the same color till it reaches the stigma, where it is widened to 

 twice its previous thickness, forming a broad blue-black margin along the 

 inner side of the stigma ; the stigma is dull white ; discoidal veins, pale 

 yellow; the first of these veins is straight, the second arises almost in 

 contact with it, and is straight nearly to its tip, where it curves slightly 

 toward the inner margin ; the third vein obsolete for about one-fourth of 

 its length at the base. Length to the tip of the abdomen about one- 

 tenth of an inch ; to the tips of the wings, one-seventh of an inch. 



yS. Pemphigus popularia, Fitch. Poplar Gall-louse. 



A species noticed, by Dr. Fitch, wandering up and down the trunk 

 of the balsam poplar, whose habits are yet unknown. It closely resem- 

 bles the preceding, but its abdomen is green ; its antennae quite short, 

 reaching but two-thirds the distance to the insertion of the wings; the 

 rib-vein not widened along the stigma ; length to the tip of the wings 

 about one-eighth of an inch. Color black, slightly dusted over with a 

 whitish powder; the abdomen dull green, with a coating of white fioc- 

 culent down; sides parallel; wings dull hyaline; the rib-vein black. 



79. Pemphigus populi-globuli. Fitch. The Poplar-bullet Gall-louse. 



This species produces a green gall about the size of a bullet, globular 

 in shape, on the leaves of the balsam poplar. These galls are situated 

 slightly above the base of the leaf, projecting from the upper surface, 

 with a curved orifice or mouth on the underside; within these reside the 

 lice, some of which are pale green, others very small and dusky, and larger 

 winged ones of a black color. These are found in this condition in July. 

 The winged individuals differ from P. popularia as follows : They are 

 uniformly smaller, wings clearer and veins more slender and colorless, 

 except the marginal vein, which is black to the stigma; the abortive basal 

 third of the third vein is traced by a very slender line, which appears to 

 be more distinct than in any of the allied species; the abdomen is dusted 



