AMERICAN GALLFLIES OF THE FAMILY CYNIPIDAE PRO- 

 DUCING SUBTERRANEAN GALLS ON OAK. 



By Lewis H. Weld, 



Of the Bureau of Entomology, United States Department of Agriculture. 



Few galls on the roots of oaks, produced by the hymenopterous 

 family Cynipidae, have ever been described. The present paper is an 

 attempt to bring the American instances together from the scattered 

 literature and to make considerable additions from the records of 

 the bureau and from the writer's personal field notes made in various 

 parts of the United States during a period of several years collecting. 

 To the seven species already described as producing underground 

 galls on oak, twenty-three new species are here added, several changes 

 made in synonomy, revisions given of four of the smaller genera, and 

 field notes included on eight additional subterranean galls not reared 

 as yet, the galls being described without name. The paper is a con- 

 tribution from the Branch of Forest Insects, Bureau of Entomology, 

 and was undertaken at the suggestion of Mr. S. A. Rohwer, specialist 

 in forest hymenoptera, to whom the writer is indebted for many 

 helpful suggestions and for access to the records and collections in 

 the Division of Forest Insects and in the United States National 

 Museum. 



Not all the species mentioned in the subjoined key to the galls 

 have been reared, but in order to make the paper as complete as 

 possible it was thought best to include these unreared galls under 

 the writer's note numbers without generic determination in order that 

 otheis may be stimulated to look for them and rear them if possible. 

 Many interesting cases of alternation of generations are no doubt 

 connected with galls on the roots of oak, and much biologic work will 

 remain to be done when all the species have been discovered. Little 

 collecting has as yet been done in the Rocky Mountain region, and 

 new host oaks will be found for many of our better known eastern 

 species. 



In order better to study the characters used in classification, a 

 specimen of each species here treated was dissected and the parts 

 mounted in balsam. 1 Drawings were then made with a projection 



i For this purpose alcoholic material can be used or pinned specimens can bo relaxed by soaking over- 

 night in 70 per cent alcohol to which some caustic potash has been added. Dissections are then made 

 under binocular, the parts being removed to 70 per cent alcohol in a watch glass. After a few minutes 

 this is drawn off by a fine pipette and replaced by absolute alcohol, then by carbol-xylol, and then parts 

 are mounted in balsam. 



Proceedings U. S. National Museum. Vol. 59— No. 2368. 



187 



