162 GALL-FLY. 



Besides the Gall-fly, properly so called, there are several 

 other insects which cause by their punctures a variety of 

 vegetable excrescences somewhat resembling those described. 

 Amongst these are the thistle-fly, 1 gall-gnat, 2 a few minute 

 beetles, and several sorts of Aphides. 



As works of wonder, all the comparatively great effects 

 which arise from these tiny causes are worthy of description, as 

 well as notice ; but they are too large and too varied for the 

 little limits of our page. It remains, moreover, to complete 

 our outline sketch of Insect Magicians by one or two of the 

 most plausible conjectures, as to the manner in which their 

 natural miracles are wrought through the prick of a needle, 

 tit only for the fingers of Queen Mab. 



The Ovipositor, or egg-inserting piercer, of the mother 

 Gall-fly, is, in some instances, conspicuously long ; in others, 

 only partially visible, except on pressure, when it appears 

 issuing from a sheath, in form of a small curved needle longer 

 than the insect's body, wherein it is, however, rolled up by a 

 curious internal apparatus. It is supposed, by Mr. Rennie, 3 

 that " after the Gall-fly has made a puncture with this instru- 

 ment, and pushed her egg into the hole, she covers it over 

 with some adhesive gluten ; or that the egg itself, as is usual 

 among moths, &c, may be thus coated over. In either of 

 these cases the gluten will prevent the sap that flows through 

 the puncture from being scattered over the leaf, and wasted ; 

 and the sap, being thus confined to the space occupied by the 

 eggs, will expand and force outward the pellicle of gluten that 

 confines it; till, becoming thickened by evaporation and 

 exposure to air, it at length shuts up the puncture, stops the 

 further escape of the sap, and the process is completed." 

 The above explanation is, however, only given as conjectural, 

 and the one generally adopted by French naturalists is, that 



1 Tephritis Cardui. * Cecidomyia. 



3 Insect Architecture, pp. 371-3. 



