INSECTS : stutgs and ovipositoes. 14.-7 



insect be gently pressed. "Wlien this is done to the fly 

 that produces the currant-gall of the oak, the ovipositor 

 may be seen issuing from a sheath in form of a small 

 curved needle, of a chesnut-brown colo\ir, and of a 

 horny substance, and three times as long as it at first 

 appeared. 



" What is most remarkable in this ovipositor is, 

 that it is much longer than the whole body of the in- 

 sect, in whose belly it is lodged in a sheath, and, from 

 its horny nature, it cannot be either shortened or length- 

 ened. It is on this account that it is bent into the same 

 curve as the body of the insect. The mechanism by 

 which this is effected is similar to that of the tongue of 

 the woodpeckers {PicidoB), which, though rather short, 

 can be darted out far beyond the beak by means 

 of a forked bone at the root of the tongue, which is thin 

 and rolled up like the spring of a watch. The base 

 of the ovipositor of the gall-fly is, in a similar way, 

 placed near the anus, runs along the curvature of the 

 back, makes a turn at the breast, and then, following 

 the curve of the belly, appears again near where it 

 originates. 



" "With this instrument the mother gall-fly pierces 

 the part of a plant which she selects, and, according to 

 our older naturalists, ' ejects into the cavity a drop of 

 her corroding liquor, and immediately lays an egg or 

 more there ; the circulation of the sap being thus inter- 

 rupted, and thrown, by the poison, into a fermentation 

 that bums the contiguous parts and changes the na- 

 tural colour. The sap, turned from its proper channel, 

 extravasates and flows round the eggs, while its surface 

 is dried by the external air, and hardens into a vaulted 

 form.' Earby and Spenee tell us, that the parent-fly 



