No. 2368. AMERICAN SUBTERRANEAN GALLS ON OAK— WELD. 235 



scattered setigerous punctures, arcuate furrow at base on which are 

 several longitudinal ridges. Propodoum with two straight carinae 

 inclosing a smooth area slightly longer than wide and wider at the 

 top and with faint median ridge. Mesopleura coriaceous becoming 

 polished on hind margin. Legs microscopically coriaceous also, all 

 last tarsal segments infuscated, tarsal claws simple. Wings clear 

 with brown veins, first and second cross-veins slightly clouded, areolet 

 present, surface pubescent and margin ciliate. Abdomen much com- 

 pressed, higher than long, smooth and polished, second segment occu- 

 pying about half the length and with a few scattered hairs on each 

 side at base. Hypop3^gium prominent, ventral spine twice as long as 

 broad, ventral valves protruding at an oblique angle, ovipositor when 

 dissected out nearly one and two-thirds as long as antenna. Using 

 width of head as a base, the length of mesonotum ratio is 1.16; 

 antenna, 2.5; ovipositor, 4.4; wing, 3.8. 



Range in length of 23 pinned specimens is 1.8-2.7 mm. Average, 

 2.1 mm. 



Type.— Cat. No. 22580, U. S. N. M. Type and 12 paratypes. 



Host. — Quercus macrocarpa Michaux. 



Gall. — Cells in the thickened bark at the crown of small sapling 

 causing an abrupt swelling of four to five times the normal diameter 

 of the shoot and extending for a distance of as far as 30 cm., or in 

 bark at base of young shoots in such numbers as to cause a notice- 

 able swelling. Almost wholly buried under the debris on forest floor. 

 Resembles the gall of the sexual generation of Callirytis futilis (Osten 

 Sacken) on roots of large trees of Quercus alba, except that cells are 

 smaller. 



Type locality. — Winnetka, Illinois. One gall was found October 

 22, 1914, and contained living adults. Another was found No- 

 vember 1, with adults emerging, and they continued to come out 

 until November 11. Another gall was found at Fort Sheridan, 

 Illinois, on October 3, 1914, and living flies were cut out of it on 

 October 29. 



33. COMPSODRYOXENUS TENUIS, new species. 



Plate 36, fig. 29. 



Female. — Species nearly black, head (except eyes) and thorax 

 being more or less brownish, antennae and tarsi still lighter brown- 

 Head broader than thorax, axial line 0.55 of transfacial, face closely 

 punctate, frons and cheeks coriaceous, broadened slightly behind 

 eyes, malar space one-fifth eye with parallel striae, interocular area 

 not as wide as high, antennocular space less than ocellocular, man- 

 dibles 2-toothed, palpi 5- and 3-segmented, antennae 12-segmented, 

 first, third, and fourth equal, 7-11 getting gradually shorter and 

 barrel-shaped, last a little over twice as long as preceding which is a 



