l88 ENTOMOLOGICAL NEWS. [April, '13 



ens, the gall wall is simply gnawn partly through, while in Gnorimos- 

 chema an aperture of exit is carefully prepared and plugged. These 

 different methods of procedure are remarkably suited to the habits of 

 the insects. In the former a plugged exit would not be suitable, 

 as the insect winters in the larval condition and the drying of the 

 gall would prevent the plug from slipping out easily. In the latter 

 the galls are still green when the insect becomes mature and the 

 plug mechanism is preferable. It is clear then, that in these galls 

 the producer is much more active in providing for its own welfare 

 than in the higher types and the plant renders a relatively smaller 

 amount of assistance .... As I have repeatedly found the open- 

 ing through which the larva of Eucosma scudderiana has entered the 

 stem [of Solidago], it is certain that this Lepidopterous producer 

 always oviposits on the outside of the host, and this may prove to 

 be true of the entire group." 



Adler found that cell proliferation on the part of the plant to 

 form saw-fly galls preceded the hatching of the saw-fly's egg and hence 

 concluded that these galls, in contradistinction to those produced by 

 other insects, owe their origin to the wound caused by oviposition. 

 Mr. Cosens obtained galls of three species of Pontania, of this family, 

 with the larvae still within the egg and here also considerable proli- 

 feration of plant tissue had already occurred. He suggests the "slight 

 possibility that secretions or excretions from the developing larva 

 may be active through the egg membrane" as the gall-forming stim- 

 ulus. 



The walls of Cynipid galls are usually differentiated into an inner 

 nutritive, and an outer "protective," zone. Adler held the latter to 

 be a defence against parasites, but Mr. Cosens found seventy-five 

 per cent, of the galls of Amphibolips coiiflucns parasitized in spite of 

 its thick epidermis and well-developed protective sheath. "Apparently 

 the only protective function that can be ascribed to this tissue is the 

 prevention of injury to the producer by desiccation during its later 

 larval and pupal stages of development." 



Gall-producing larvae differ in their habits of feeding on the gall 

 tissue. In the Acarina (Eriophyidae), Hemiptera (Aphididae, Psyl- 

 lidae), Diptera (Cecidomyidae, Trypetidae) and Cynipidae (but not 

 inquilines), the cell contents alone furnish the nourishment and these 

 are withdrawn from the cells without destroying the cell-walls. On 

 the other hand, Lepidopterous, Coleopterous, and Tenthredinid gall- 

 producing larvae, and at least some inquiline Cynipid larvae, devour 

 both the cell-walls and the cell-contents. Mr. Cosens made experi- 

 ments showing that the larvae of the Cynipid Amphibolips confluens 

 secretes a salivary gland enzyme which changes starch to sugar; he 

 holds that this ferment "must act through the cell membrane lining 



