57S TRANS. ST. LOUIS ACAD. SCIENCE. 



were badly trodden, that full two-thirds of the cups observed were affected. 

 Those which I have opened still contain the larva." 



I have seen it on j^. prinoides and J^. bicolor* The parent 

 Cynips lays the egg very early in summer, as the gall is often 

 formed on the aborted or blighted acorns, in which case, how- 

 ever, it seldom attains perfection. The ripe and well developed 

 gall falls out of its cavity on to the ground, where the larva 

 remains within it till the following spring. Those galls which 

 remain within the cavity are generally imperfect. The fly pro- 

 ducing this gall has not yet been reared nr described. 



Cynips Gall ^uercus-glandulus : — An elongate, pip-like body, averag- 

 ing, when well developed, 5 mm. long, and not quite half as wide; sides 

 sometimes parallel, but more often slightly bulging, more or less deeply 

 corrugate longitudinally, and whitish-green; base truncate and covered 

 with whitish down ; crown flattened or slightly concave, with a central, 

 conical nipple; color yellowish, often with a roseate tint. Larva lying in 

 a cell near the crown. Formed in a cavity, and causing more or less bulg- 

 ing and swelling of the cupule. The mouth of the cavity either strongly 

 fimbriated, or simple, according to the nature of the cup scales, and thus 

 either hiding the gall or exposing a large part of it. 



This gall is allied in structure to that described by Mr. Bassett 

 as Quercus frondosa (Proc. Ent. Soc. Phil. iii. p. 6SS), which 

 is a deformation of an oak bud. The axillary bud is made by the 

 sting of the Cynips to prematurely develop a number of lanceolate 

 or ovate leaves which surround one or more cells, which loosen 

 from their leafy matrix when ripe and drop to the ground. An ana- 

 logous deformation of an oak bud, caused by Cynips fecundatrix 

 Hartig, is very common in Europe, and is known in England as 

 the Artichoke-gall. The cell of this gall has been described as 

 an aborted acorn by Mr. Albert Miiller,f who has made a special 

 study of galls. It is not surprising, therefore, that our glandulus 

 gall should very generally be looked upon as a diminutive or sec- 

 ondary acorn. Yet such views are quite erroneous. The cells of 

 very many other Cynipidous galls resemble acorns in form, and 

 the resemblances to different fruits among these singular plant- 

 and-insect productions is often so striking as to easily mislead. 



* Dr. Engelmann has noticed it on ^>. Prinus, &>. Michauxii, and jg. Muhlenberg ii. 

 It thus occurs on every form of the Prinus Group, to which it is apparently conrined. 

 t Jour, of Linn. Soc. (London) Zoiil., vol. xi. p. 3. 



