PERGANDE — NORTH AMERICAN PHYLLOXERINjE. 203 



shade; the two branches are much farther apart than is usual, on 

 account of the stigmal vein, which is far removed to the apex 

 of the stigma. The bases of both branches are often completely 

 obliterated and without a connection with either the discoidal or 

 the stigma. , 



Phylloxera pilosula Pergande, n. sp. 

 PI. III., fig. 17; PI. IX., fig. 49. 



The galls of this species are very unique and readil5r dis- 

 tinguished from an}- others so far observed. They occur 

 usually on solitary trees of Hicoria glabra along the Potomac near 

 Washington. They are usually quite abundant though rather 

 sparsely dietributed, there being but one, or rarely more than 3-6, 

 upon a leaf and seldom so close together as to become confluent. 



When first found, May 23rd, they wer° already fully devel- 

 oped, but contained, besides the stem-mother, only eggs and 

 larvae. Ten days later most of the insects had already acquired 

 wings. 



The transverse diameter of the gall varies between 3-6"""-, and 

 their height to the tip of the nipple 2-3"""-. They are quite flat 

 above, even with the surface of the leaf or but slightly projecting 

 above it. In the latter case they are usually surrounded by a 

 somewhat depressed ring and have a slight inclination to one 

 side. There is always a more or less distinct shallow depression 

 at the middle, which is usually quite densely covered with rather 

 long, faintly yellowish, soft and glistening hairs. On the under 

 side they resemble somewhat those of the variety Ph. c. -symmet- 

 rica, though they are more evenly convex and provided with a 

 rather long and slender nipple, which is split into five to six, or 

 rarel}' more, slender filaments, which usually lean to one side. 

 This nipple, as well as the surface of the gall, is quite densely 

 covered with long, glistening and faintly yellowish hairs similar 

 to those on the upper surface. This pilosity of the gall is quite 

 in contrast with the otherwise perfect smoothness of the leaves 

 above and beneath. The upper side of the galls is of a paler 

 green than the leaf itself, with a slight tinge of yellow, whilst on 

 the underside the color merges gradually from pale green at its 

 circumference to almost white at the nipple. The walls are quite 



