OF THE FAKM AND aAEDEKT. 253 



The Root-inhabiting Type {Radicicola). — We have 

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

 wingless, shagreened, non-tubercled, fecund female 

 form. Radicicola, however, presents itself in two prin- 

 cipal forms. The newly hatched larvas 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 

 development 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 (b) of a brighter yellow, with the 

 lateral outline more perfectly oval, and with the abdomen 

 more truncated at tip. 



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

 logue of gallicola, as it never acquires wings, 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 have counted in the spring 

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

 and all evidently from one mother, who was yet very 

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

 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, suture^, and 

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

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

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

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

 domen. 



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

 to become winged. Its tubercles, when once acquired, 

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

 and its eyes increase rather than diminish in complexity 



