158 TRANSACTIONS OF THE 



"with or without spinning a cocoon. The pupae of those species 

 ■which pass that state inside hard galls, for example G. Salicis, are 

 provided with a tooth-like process at the root of each antenna by 

 means of which they force their way out, when about to assume 

 the perfect state. 



Having treated of the Insect — the gall-maker — I now turn to 

 its production the Gall. This I described as that change of struc- 

 ture brought about by the puncture or irritation of the gall-maker. 



The Cynipidse and Cecidomyidse seem broadly and markedly 

 contrasted in the making of the gall. In the Cynipidse the gall is 

 formed — often fully developed — before the egg is hatched. In 

 the Cecidomyidse it is very different. The eggs are deposited deep 

 down in the interstice between leaf-stalk and stem, or other 

 sheltered nook ; here it is hatched and sometimes has to travel to 

 the seat of its operations, but no gall is formed by the parent-fly ; 

 it is due to the irritation of the larva itself, which thus builds its 

 own dwelling. 



The irritation of the larva takes effect in one or both of two 

 ways. It excites abnormal activity in the formative powers of 

 the plant at the place affected, resulting in a thickening or 

 enlargement of the parenchyma, an increased fleshiness ; or in the 

 excessive development of such epidermal appendages as hairs ; or 

 in regular outgrowths. Secondly, it causes an arrestment of growth 

 in certain directions. 



We may classify galls according to the part of the plant upon 

 which they are found j upon the root, stem, bud, or leaf. Bud 

 galls we may divide into terminal, axillary, and flower-bud galls. 

 Leaf galls we may divide into leaf-rollers, leaf-folders, and leaf 

 galls proper. 



I have paid some attention to the dipterous gall-makers of the 

 Glasgow district, but as in many cases I have not been able to 

 rear the maker of many galls I have met with, I have thought it 

 better to give here a list of the galls only, taking the plants in 

 their botanical order, and leaving any detailed account of the 

 makers till a future occasion when my material is more complete. 

 This list will sei've another purpose, in drawing the attention of 

 the botanical membsi's of our Society to the subject. I shall be 

 only too glad to receive any galls they may meet with in their 

 searches for plants, especially any found upon the Carices and 

 Grasses and also upon the Cruciferas and Umbelliferse. 



