lo British Vegetable Galls 



succulent gall 24 mm. long and 70 mm. at its greatest girth, 

 whereas the same number of larvae of Urophora solstitialis living 

 at the base of a flower-head of Centaurea nigi-a will cause a 

 hard and woody gall 10 mm. high and 20 mm. in girth, con- 

 siderably less than half the bulk of the other. The imagines of 

 both species are the same size. 



One larva of Honnomyia Fagi will cause a hollow cone- 

 shaped gall on a leaf of Fagus sylvatica 4 mm. high and 4 mm. 

 in girth at its base ; one larva of AspJwndylia pimpcrnellce will 

 cause a hollow, reniform gall 8 mm. long and 15 mm. at greatest 

 girth on the umbels of Dancus carota. There is scarcely any 

 difference in the size of these imagines. 



Of all gall-producers the Eriophyida live together in greatest 

 numbers. A leaf-bud of Corylus Avellance or Ribes nigrum 

 in the summer time will contain hundreds of the creatures 

 in each of their stages of growth ; while on such masses of 

 deformed and stunted growth as illustrated in plate 62, the 

 mites would possibly number hundreds of thousands. 



The number of separate cells, or larval chambers, varies 

 greatly. A large proportion of galls are unilocular, and are 

 seldom of any remarkable size, but the largest number are 

 multilocular. Most of the latter kind are composed of 3 to 8 

 cells ; but in Rhodites roses there may be from 30 to 50, Atdax 

 papaveris 40 to 60, and Diastrophus riibi 80 to no. These 

 cells are all included within one outer covering, whether it 

 be a coating of long hairs, a seed capsule, or the epidermis 

 of the stem. 



The smallest unilocular gall is the pustule form caused by 

 Eriophyes macrorhyncus. They are very numerous on the 

 leaves of Acer campestre. The largest is that caused by 

 CeiitJiorhynchus siilcicollis on the root of Brassica ttapus. The 

 gall caused by Lipara lucens on Anindo Phragmites would 

 appear to be larger, but its additional bulk is due to the 

 numbers of leaves which enfold one another, and enclose a 

 relatively small larval chamber. 



The shapes of galls vary greatly. About eighteen definite 

 forms can be recognised. 



Globular, or more or less so, is the shape of the majority. 

 Many are reniform, not only as a single growth {^Eriophyes 

 macrocJichis), but in clusters {Xestopha/ies brevitarisis) on a 



