132 



THE ENTOMOLOGIST. 



notwilhstanding its production on varied organs of the plant, 

 1 may say 1 have found galls of this species on the side veins, 

 midrib, and leaf-stalk of the leaHet (upper and under side) ; 

 on the petiole and stipule of the leaf; and even once on the 

 fruit of Rosa canina: all perfectly normal forms. The con- 

 stant modifications of this gall are two, both curious and 

 interesting. Firstly — the whole interior becomes grown-up and 

 irregularly filled with chambers; for section see fig. y: the only 

 outward sign is the gall becoming brown and covered with 

 small scattered knobs. Secondly — the normal central cavity 

 remains, but the wall of the gall becomes thickened and regu- 

 larly divided into chambers; a section of a good specimen 

 of this modification, with the peripheral chambers complete, 

 is particularly striking and pretty : see fig. &. The specimens 



Fig. a. Fig. jS. Fig. y. 



are often abnormally large and, like the former, become 

 discoloured, and the surface becomes less glabrous and more 

 or less warty. These two modifications are due to a similar 

 cause with those in the oak species, viz., the tenancy of 

 phytophagous individuals. I am unable, at present, to say 

 whether they are both attributable to the same species, (or 

 from specimens of both forms I have bred Aulax canina, 

 Eurytoma sp., and various parasites. Auhix, which is closely 

 allied to Syneryus and has doubtess the same economy, is 

 the primary cause of the modification; but as to the 

 Eurytumid(B it is an undecided question whether they are 

 vegetable or animal feeders in the larval state. 



Tiie dwarfing ot all galls through inquilinism and parasitism 

 is well known and self-explanatory ; but a consideration of 

 the above-mentioned forn)s vvitii those peculiar growths, 

 mentioned in "Considerations of Gall-growth," niay lead to 

 some knowledge of the interesting, though still obscure, 

 subject — the cause and growth of vegetable galls. In the 

 animal kingdom we know that different irritants produce 

 distinctly characterised effects, so in the vegetable kingdom 

 we know that different species of insects produce different 



