232 DAVENPORT ACADEMY OF SCIENCES. 



Phyli^oxbra symmetrica n. sp., Pergande. 



TYPICAL FORM. 



This gall forms always on the under side of the . leaf ; it is 

 quite flat on the upper side, or slightly convex, occasionally some- 

 what depressed at the middle, circular, with its margin generally 

 more or less deeply sunken below the plane of the leaf and gen- 

 iprally concolorous with the upper side, or of a somewhat darker 

 shade. On the under side, however, it is quite prominent and 

 regularly conical in shape, with an opening at the tip, which, 

 however, is tightly closed till the time arrives for the migrants to 

 leave. At this time the apex commences to split into 4-8, more 

 or less slender, backward-curved bracts or filaments, surrounding 

 a more or less circular opening. The color of the lower side of 

 the galls is either that of the leaf or somewhat paler, though 

 rather darkest towards the apex, and their surface covered rather 

 sparsely with the peculiar hairs and pellets of resin so character- 

 istic of the under side of the leaves, becoming more dense 

 towards the apex. The walls of this g'all are rather stout and 

 of a dense and firm texture, increasing in thickness toward the 

 base. The transverse diameter above ranges between 2-5™™' and 

 the vertical diameter from 3-4""°-. After the insects have left, 

 the galls gradually dry up, become brown, lose their shape and 

 disappear at last almost completely. 



In this connection it will be interesting to record here what 

 appears to be a second crop of galls of probably the same 

 species, though it is quite possible that later observations may 

 prove this to be distinct. 



On the 29th of July, 1883, while examining a solitary young 

 hickory tree near the fair-ground, in the District of Columbia, 

 standing at a distance of between 20-50 feet from the nearest 

 trees of its own kind, it was observed that considerable numbers 

 of young galls had formed on the uppermost and youngest leaves, 

 which, to all appearance, could scarcely be older than, perhaps, 

 two or at most three weeks. A further examination of the older 

 leaves proved that they had been infested quite profusely by 

 galls of the species under consideration, all of which were empty 

 and more or less dried up, though a few were still on the upper 



