422 CONNECTICUT GEOL. AND NAT.. HIST. SURVEY. [Bull. 



bark when fallen off reveals a surface which is dotted as thickly 

 as possible with very small, open, larval cells to the number of 

 several hundreds ; the cells are distinct from the woody fibre in 

 which they are imbedded but cannot be separated from it. These 

 galls are easily taken for those of ^. scitulus, 

 *A. piger Bassett. Oak Midrib Gall. 



Female : length nearly 3 mm. ; mostly deep black, ocelli incon- 

 spicuous in the rather coarsely rugose vertex, antennae 14- jointed, 

 the first joint club-shaped, second ovate, third not quite as long 

 as the first and second combined, fourth, fifth and sixth subequal, 

 the remaining joints scarcely shorter than the sixth and sub- 

 equal, base clear yellowish brown, changing gradually to a 

 light dusky brown toward the apex; thorax finely and evenly 

 punctate, in a favorable light seeming to have two extremely faint 

 parallel lines which extend half-way from the pronotum to the 

 scutel, a smooth groove beginning at the scutel on the middle 

 of the mesonotum, and ending suddenly as a groove but continuing 

 as a faint depression half-way to the pronotum, the parapsidal 

 grooves fine and narrow but distinct, a smooth polished line over 

 the base of the wings, the scutel round and rugose, the foveae 

 large and deep ; the legs rather a dark reddish brown ; the wings 

 hyaline, with sharply defined veins, a small areolet and open 

 radial area and a colorless cubitus; abdomen polished and shin- 

 ing, first segment more than equal in length to the remaining ones 

 combined, sheath of the ovipositor dark yellowish brown at the 

 tip. 



The galls of this species are large, irregular swellings on the 

 midrib of the leaves of Quercus tinctoria, always on the under 

 side and usually on the lower half of the leaf ; sometimes two dis- 

 tinct galls are found on the same leaf, their presence being indi- 

 cated on the upper surface by a widening of the midrib and a 

 slight depression of the leaf at that point. They are often 25 

 mm. in length, and in the middle half 25 mm. in diameter, taper- 

 ing more or less towards the ends. They are of a dense cellular 

 tissue, with the woody fibre of the midrib along the axis. The 

 cellular portion contains a large number of larval cells, which 

 are inseparable from the enveloping substance. The galls are 

 found on young oaks early in June. They answer, it might be 



