OF THE FARM AND GAEDEl^. 



253 



The Eoot-ikhabitii^g Type {Radicicola). — We liaye 

 seen that, in all probability, gallicola exists odIj in the 

 wingless, shagreened, non-tubercled, fecund female 

 form. Eadicicola^ howexev, presents itself in two prin- 

 cipal forms. The newly hatched larya3 of this type are 

 undistinguishable, in all essential characters, from those 

 hatched in the galls; but in due time they shed the 

 smooth larval skin, and acquire raised warts or tubercles 

 which at once distinguish them from gallicola. In the 

 deyelopment from this point the two forms are separable 

 with sufficient ease: one (a) of a more dingy greenish- 

 yellow, with more swollen fore-body, and more tapering 

 abdomen; the other (e) of a brighter yellow, with the 

 lateral outline more perfectly oyal, and with the abdomen 

 more truncated at tip. 



The first or mother form (fig. 154, /, (/), is the ana- 

 logue of gallicola, as it neyer acquires wdngs, and is oc- 

 cupied, from adolescence till death, with the laying of 

 eggs, which are less numerous and somewhat larger than 

 those found in the galls. We haye counted in the spring 

 as many as two hundred and sixty-fiye eggs in a cluster, 

 and all eyidently from one mother, who was yet yery 

 plump, and still occupied in laying. As a rule, howeyer, 

 they are less numerous. With pregnancy this form be- 

 comes quite tumid and more or less pyriform, and is con- 

 tent to remain with scarcely any motion in the more 

 secluded parts of the roots, such as creases, sutures, and 

 depressions, which the knots afford. The skin is dis- 

 tinctly shagrcened (fig. 154, h,) as in gallicola. The 

 warts, though usually quite yisible with a good lens, are 

 at other times more or less obsolete, especially on the ab- 

 domen. 



The second or more oyal form (fig. 154, e), is destined 

 to become winged. Its tubercles, when once acquired, 

 are always conspicuous; it is more actiye than the other, 

 and its eyes increase rather than diminish in complexity 



