42 British Vegetable Galls 



The ravages of this species in the bulbous portion of the 

 root of the common turnip and also that of the swede turnip 

 are sometimes very considerable. They do not, however, greatly 

 diminish the value of the turnips ; but sometimes the rapid 

 decay of a root is due to moisture getting in the cavities after 

 the larvae have vacated them. The tap-root is not often galled, 

 although the root-fibres are frequently caused to swell to enor- 

 mous proportions (see plate lo). The gall-growths assume the 

 shape of mammillatcd protuberances or warty excrescences. 

 They are variable in number, some roots having but very few, 

 others as many as forty. They are mostly separate from each 

 other ; occasionally, however, several will coalesce, especially 

 when there are many galls on a root. The author has seen an 

 example in which fifteen had coalesced. 



The specimen in the illustration measured 9J in. in girth 

 immediately beneath the row of galls; iii in. over the top of 

 them ; and 13^ in. in girth in its vertical circumference. The 

 tap-root was i^ in. long. It had upon it twenty-three well- 

 defined larval chambers, ten of which can be seen. 



The larva is apodus, and lies in the cavity it makes by 

 feeding on the gall-substance, with head and tail close together, 

 after the manner of a Cynips larva. When fully fed it eats a 

 way out and pupates in the earth, particles of which it uses 

 in the formation of the cocoon. 



The specimen illustrated was taken out of a field near 

 Hastings by the author. 



