401 



Chapter XX. 



Animal Galls,* produced by Breeze-Flics and Snail-Beetle.. 



The structures which we have hitherto noticed have 

 all been formed of inanimate materials, or at the 

 most of growing vegetables ; but those to which we 

 shall now avert are actually composed of the flesh 

 of living animals, and seem to be somewhat akm to 

 the galls already described, as formed upon the 

 shoots and leaves of plants. These were first inves- 

 tigated by the accurate Vallisnieri, and subsequently 

 by Rtfaumur, De Geer, and Linnaeus ; but the best 

 account which has hitherto been given of them is by 

 our countryman Mr. Bracey Clark, who differs essen- 

 tially from his predecessors as to the mode in which 

 the eggs are deposited. As, in consequence of the 

 extreme difficulty, if not the impossibility, of personal 

 observation, it is no easy matter to decide between 

 the conflicting opinions, we shall give such of the 

 statements as appear most plausible. 



The mother breeze-fly (Oestrus bovis, Clark ;— 

 Hypoderma bovis, Latr.), which produces the tu- 

 mours in cattle called wurbles, or wormuls (quasi, 

 worm-holes), is a two-winged insect, smaller, but 

 similar in appearance and colour to the carder-bee 

 (p 64), with two black bands, one crossing the 

 shoulders and the other the abdomen, the rest being 



* In order to prevent ambiguity, it is necessary to remark that 

 tl.e excrescences thus called must not be confounded With the 

 true galls, which are occasionally found in the gall bladder. 



