CYNIPS QUERCUS FOLII. 



difficult to conceive how the insertion of so minute a body as 

 the egg of the Cynips should cause so singular a divergence 

 from the ordinary growth of the part. The simple puncture 

 and the mere mechanical irritation are not sufficient to ex- 

 plain the phenomenon in a satisfactory manner; therefore it is 

 thought that some acrid secretion is injected from the ovipos- 

 itor along with the egg, which, acting locally, like any other 

 acrid lymph which in the animal body produces a specific 

 change in the structure of the part, is the chief cause of the 

 irritation. Not the least singular circumstance is the rapidity 

 of the growth of the gall, which, however large, attains its 

 full size in a couple of days ; and this is another reason for 

 supposing that there is some fluid injected along with the 

 egg, as the larva is not yet hatched. After a certain period 

 the egg enlarges, the larva is hatched, and derives its nour- 

 ishment from the gall ; after some time it eats its way out 

 of the prison, which then becomes lighter and contains much 

 less of the astringent principle ; the galls, therefore, that have 

 a hole in them, are less valuable than the entire galls. The 

 best galls are gathered before the fly has issued from them, 

 and from galls of this kind very perfect specimens of the in- 

 sect are frequently procured. 



The oak on which the best galls are formed is the Quercus 

 infectoria, a small, tortuous tree belonging to the natural 

 order Cupuliferce, and is thus described by Olivier. It has a 

 crooked stem, seldom exceeds six feet in height, and more 

 frequently assumes the character of a shrub than that of a 

 tree. The leaves, which are deciduous in autumn, are on 

 short petioles, smooth, of a bright green color on both sides, 

 and obtusely toothed ; the acorn is elongated^ smooth, two or 

 three times longer than the cup, which is sessile, in a slight 

 degree downy, and scaly ; the gall comes at the shoots of the 

 young boughs, and acquires from four to twelve lines in di- 

 ameter. Never more than one ovum is deposited in the gall, 

 this fetal habitation being what entomologists term mono- 

 thalmous. 



The best galls are those of Aleppo, Smyrna, Magnesia, 

 Karahisser, Diarbekir, and the interior of Natolia. They are 

 termed black, green, or blue galls ; those through which the 

 insect has eaten its way out are called white galls. The galls 

 formed on the Quercus robur, Quercus cerris, and other spe- 

 cies of oak, are small, smooth on the surface, polished, reddish, 



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