406 Insect Architecture. 



theory be adopted, it will be obvious that their growth must 

 be rapid ; for the thickening of the exuded sap, which is 

 quickly effected by evaporation, will soon obstruct and 

 finally close the orifice of the puncture made by the parent 

 insect. It is accordingly asserted by Eeaumur and other 

 observers, that all the species of galls soon reach their full 

 growth. 



A very minute reddish-coloured grub feeds upon dyer's 

 broom (Genista), producing a sort of gall, frequently globular, 

 but always studded with bristles, arising from the amor- 



Leafy Gall of Dyer's Broom, produced by Cynips genista f A, gall, natural size ; 

 B, a leaflet magnified. 



phous leaves. The stem of the shi*ub passes through this 

 ball, which is composed of a great number of leaves, shorter 

 and broader than natural, and each rolled into the form of a 

 horn, the point of which ends in a bristle. In the interior 

 we find a thick fleshy substance, serving to sustain the leaves, 

 and also for the nourishment of the grubs, some of which are 

 within and some between the leaves. They are in pro- 

 digious numbers, hundreds being assembled in the small 

 gall, and so minute as scarcely to be perceived without the 

 aid of a magnifying glass. The bud of the plant attacked 



