1912] Morphology and Biology of Insect Galls 313 



"Some observers say the interior of the gall is lined with silk. I 

 have never found this, but preparatory to the exit, the mature larva be- 

 fore pupating constructs a silken hammock in the upper end of the gall, 

 and opposite the aperture of exit. The larva resting in this hammock 

 bites out a hole to the epidermis of the gall which is carefully left. The 

 hole is bevelled towards the outside, and then neatly filled up with the 

 material gnawed out, mixed with a silk-like substance, doubtless from a 

 gland, which forms a tight-fitting, hard plug which cannot be pushed in 

 from the outside but is easily pushed out from the inside." — Brodie." 



The anatomical features of this gall are very similar to those de- 

 scribed in the Eucosma species. The gall mass is produced by the radial 

 increase in thickness of the bundles and the growth into the gall cavity 

 of the intervening parenchymatous strands seen in Fig. 20. There is 

 gr iater proliferation of the cortical tissue in this case than in that of the 

 Eucosma gall and the cells produced are much larger than those found 

 in the normal stem. 



The remarks concerning the gland production and distribution of 

 the preceding species are also applicable to this form. 

 Gnorimo schema gallceasterella Kellicott. 



"In a collection of galls made May 29, 1890, a few miles north of 

 Toronto, most of them were at the top of the stem, surmounted by a few 

 leaves, occasionally but one, usually two. The galls at this date seemed 

 to be mature, sub triangular, corresponding to stem of plant; from 20 

 mm. to 32 mm. long, and from 10 mm. to 15 mm. diameter. In size, 

 form and structure the galls closely resemble the galls of G. gallcesolida- 

 ginis Riley. Rarely they occur on the middle and lower third of the 

 stem of the plant." — Brodie." 



"The gall produced on SoUdago ccBsia var. axillaris Gray by this 

 producer is quite unlike the S. latifolia gall in appearance, but as both 

 galls are merely spindle-shaped enlargements of the stems of the host 

 plants, this difference in outward form can easily be explained. The 

 glaucous, terete and slender stem of S. ccesia produces a gall with glaucous 

 epidermis, circular in cross section and gradually tapering towards each 

 end. On the other hand, the smooth, angled and comparatively thick 

 stem of S. latifolia gives rise to a gall with smooth epidermis, somewhat 

 triangular in cross section. This gall has also a greater diameter and 

 tapers more abruptly than the 5. c(Bs:a gall." — Cosens.^^ 



The anatomy of this gall presents the typical structure of a gall of 

 the Lepidopterous class. The cortex of the stem does not play an im- 

 portant r61e in the production of the abnormal tissue; but when the 

 host plant is SoUdago latifolia L. the gall cortex is thicker than that of 

 the normal stem. As in the case of the gall produced by G. gallasoli- 



