1865.] Ml 



brittle shell, containing a proportionally small central nucleus, kept in 

 position either by a spongy matter, filling up the space between it and 

 the shell, or by filaments, radiating from it. It is in this group that 

 the dimorphism of a female (that of C. spongifica ) was first discovered 

 by Mr. Walsh, and it would be an interesting and comparatively easy 

 subject for observers to investigate, whether the other species of the 

 group likewise have dimorphous females? It would be sufficient, I 

 think, to use for this purpose the same process which Mr. Walsh has 

 used for the discovery of the dimorphism of (J. spongifica, that is, to 

 collect a large number of galls at the proper time in the spring or in 

 early summer, and thus to obtain the two successive broods, the bisexual 

 one in summer and the dimorphous female brood in winter or early 

 next spring. I should not wonder at all if, in some cases, the galls 

 producing the dimorphous females were somewhat, or perhaps even 

 altogether, different from those producing the bisexual brood. Is not 

 C. formosa Bassett, known in the female sex only and bred in winter, 

 a dimorphous female of some other species? It is distinguished from 

 the sexual females of the genus by precisely the same characters which 

 distinguish O. aciculata (the agamous female of C. spongifica^) ; its 

 abdomen has the same shape as C. aciculata, and is different in shape 

 from the abdomen of the sexual females; its sculpture, like that of C 

 aciculata, is less coarse than that of the sexual females, and also distin- 

 guished by five aciculate striae ; its antennas have more joints than 

 those of the sexual females. 



6. C. modesta 0. S., 0. quercus nigrse 0. S. and C. tumifica O. S. 

 form again a distinct natural group, remarkable for the absence of the 

 areolet, the peculiar, microscopic sculpture of the thorax, rendering it 

 opaque, and the great difference in size and color between the two 

 sexes. Their galls are polythalamous swellings of the leaf-ribs, contain- 

 ing many small, seed-like bodies. They occur on Q. rubra, tinctoria 

 and nigra. 



7. 0. operator 0. S. with 12-jointed 9 antennas and some other pe- 

 culiarities, will probably form a new genus. It occurs on Q. nigra, and 

 the same species or a similar one on Q. palustris and ilicifolia. A pe- 

 culiarity in the neuration constitutes a point of relationship between 

 this species and G q. phellos and C. similis, which, however, are dis- 

 tinguished by the sheath of the ovipositor being much less protruded. 



8. 0. punctata Bassett (podagrae Walsh) is apparently agamous ; 

 more than 120 £ specimens were reared by MM. Walsh and Bassett, 

 without a single male. If such is the case, we have before us an aga- 

 mous species, the thorax of which is not pubescent, as the thorax of the 



