1914 ENTOMOLOGICAL SOCIETY. 103 



starch to sugar, and has also demonstrated the presence of salivary glands opening 

 externally in Philonix nigra Gillette (Fig. 11), and Amphibolips confluens 

 Harris. We may conclude, then, that at least one enzyme is present in the salivary 

 secretion of the larvas of tlie Cynipidae and that this acts as a pre-digestive ferment 

 on the contents of the nutritive zone. By its action, starch is changed into a readily 

 soluble substance, and is consequently readily absorbed by the digestive tract of the 

 larva. 



The fact that excrement is not found in Cynipid galls has formerly been 

 explained by the assumption that the alimentary canal of the larva ends blindly. 

 As the writer has demonstrated its completeness in Philonix nigra Gillettee (Fig, 

 10), and Amphibolips confluens Harris, this is probably the case in all of the 

 species. The correct explanation for the absence of frass is that the larva uses as 

 food only the cell contents of the nutritive zone, and these have been rendered 

 capable of complete absorption by the amylalytic ferment in the larval secretion. 

 A very marked feature of the nutritive zone of the galls is the gradual collapsing 

 of the cells as their contents are removed. Compare Figs. 6 and 7. Since the cell 

 walls lining the Cynipid larval chamber are not broken by the larva in feeding, 

 the interior of the cavity remains smooth, a marked contrast to the ragged, broken 

 edge of tissue left where an inquiline larva has been feeding. A comparison of 

 Figs. 8 and 9 will demonstrate this. The difference in the nature of the food is 

 shown in the stomach contents of the Cynipid and the inquiline larva. The former 

 coiisists of a mass of extremely fine particles, among which can be detected nothing 

 tliat is recognizable as having formed a part of a cell (Fig. 8). but the latter is 

 composed of much coarser material in v/hich crystals and parts of cell walls can be 

 easily detected (Fig. 9). 



As well as thus acting as a pre-digestive factor the ferment in the larval sali- 

 vary secretion has an indirect action on the production of the gall. Owing to its 

 influence the nutritive zone will become stored with an unusually large amount of 

 available nourishment which can diffuse to all parts of the gall. The protoplasm of 

 the latter is thus rendered unusually active, since it receives an abnormal quantity 

 of available food material in a limited area. The hypertrophy and cell prolifera- 

 tion and probably also the appearance of vestigial tissue, or other primary characters 

 are explainable as the response of the protoplasm of the host to the additional food 

 supply. 



Descbiption of Plates 2 and 3. 



Fig. 1. Rhahdophaga triticoides Walsh on the stem of Salix cordata Muhl. Transverse 

 section of a young gall. In which is shown the general arrangement of the larval cham 

 bers and the distribution of aeriferous tissue throughout the cortex and pith of the gall. 

 The edges of three larval chambers are bounding the pith of the gall. X^O. 



Fig, 2. Eurosta solidaginis Fitch on the stem of SoUdago canadensis L. Transverse 

 section showing the proliferation of glandular tissue. X^S. 



Fig. 3. Cecidomyia ocellaris O.S. on the leaf of Acer rubrum L., showing the almost 

 unchanged character of the leaf immediately below the larva, and the great amount 

 of proliferation in the region surrounding it. X^O. 



Fig. 4. Eriophyes sp. (Fagus grandifolia Ehrh.) Section through a number of 

 capitate trichomes. The almost normal character of the leaf is shown. X^O. 



Fig. 5. Eriophyes sp. (Acer negundo L.) Section through the gall, showing a large 

 number of convoluted trichomes. X^S. 



Fig. 6. Dryophanta palustris O.S. on the leaf of Quercus vehitina Lam. Section of a 

 very early stage in which the inner and outer galls are still in contact. X^O. 



Fig. 7. Dryophanta palustris O.S. on the leaf of Quercus velutina Lam. Section of 

 the larval chamber of a mature specimen, showing the insect breaking out of the Inner 

 gall. At this stage the nutritive layer has entirely collapsed, xl^- 



