218 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.59. 



tate pubescent patch on either side of base of second segment, a very 

 few hairs on exposed part of seventh. Ventral spine in balsam three 

 times as long as broad, ovipositor when dissected out equal to length 

 of antenna, ovarian eggs well developed. Using width of head as 

 base, the length of wing ratio is 3.6-3.8; mesonotum, 1.5; antenna, 

 2.0-2.2; ovipositor, 2.1-2.2. 



Range in length of 40 pinned specimens is 4.2-4.8 mm. Average, 

 4.5 mm. 



Runs in Dalla Torre and Kieffer's key (1910) to Callirliytis radicis 

 Bassett, from which it may be distinguished by the larger size, 

 longer pubescence on wing, and presence of white pubescence on body. 



Type.— Cat. No. 22568, U.S.N.M. 20 cotypes. 



Host. — Quercus alba Linnaeus, Quercus macrocarpa Michaux, 

 Quercus bicolor Willdenow, Quercus prinus Linnaeus. 



Gall. — A large rounded mass, 90 by 50 by 50 mm. or smaller, grow- 

 ing out from side of one of main roots at base of tree or stump just 

 below surface of the ground. Surface uneven but smooth, brown. 

 When mature the interior is soft and easily cut or crumbled with 

 the fingers, and might be taken for a piece of well-rotted wood until 

 he numerous hard shell-like thin-walled brown cells are noticed 

 mbedded in the whitish matrix. When the moisture is dried out 

 the galls are as light as cork. 



Type locality. — Fort Sheridan, Illinois. 



Biology. — On October 4, 1914, galls were found on Q. macrocarpa 

 with adults ready to emerge; others with the substance of the gall 

 firmer contained full-grown larvae, others less than half an inch in 

 diameter were fleshy with larval cavities barely visible, suggesting 

 that the gall takes three years to mature, or else two, and the larvae 

 in some do not transform the second fall but hold over until the 

 third. At Winnetka, Illinois, October 30, some galls contained 

 adults and others were very small. On November 1, immature 

 galls were found at New Lenox, Illinois. On April 24, 1915, a small 

 gall was found on Quercus alba from which adults were issuing. 

 They were smaller, averaging 3.4 mm., but otherwise similar. Found 

 gall at Highland Park, Illinois, on May 12, 1917, looking as if the 

 adults had but recently issued; another at Fort Sheridan May 25 

 showed exit holes where all the adults had escaped. Collected a 

 fine gall on Quercus alba May 6, 1914, on Plummer Island, Maryland. 

 Adults evidently transform in autumn and emerge the next spring 

 in late April or early May. A single fly of what seemed to be this 

 species was noted in the stomach contents of blue-headed vireo 

 (Lanivireo solitarius (Wilson) at Washington, District of Columbia, 

 on April 15. A single old gall of this species was found on roots of 

 Quercus prinus in September, 1919, at East Falls Church, Virginia, 

 and another at Plummer Island, Maryland. 



