INSECTS: STINGS AND OVIPOSITORS 151 



look like bunches of green currants often seen growing 

 on the oak, are not the proper fruit of the tree, but dis- 

 eased developments produced by a tiny insect, for the 

 protection and support of her young. But perhaps you 

 have never paid any special attention to the living atom 

 whose workmanship they are, and are not familiar with 

 the singular mechanism by which she works. I have not 

 had an opportunity of seeing it myself, and therefore can- 

 not show it to you ; but as Gall-flies are by no means rare, 

 and you may easily rear a brood of flies from the galls, 

 you may have a chance of meeting with it. I will there- 

 fore quote to you what Rennie says about it. 



"There can be no doubt that the mother gall-fly makes 

 a hole in the plant for the pur- 

 pose of depositing her eggs. 

 She is furnished with an ad- 

 mirable ovipositor for that ex- 

 press purpose, and Swammer- 

 dam actually saw a gall-fly 

 thus depositing her eggs, and 



we have recently witnessed the OALL-FLY AND MECHANISM OF OVIPOSITOR. 



same in several instances. In some of these insects the 

 ovipositor is conspicuously long, even when the insect is 

 at rest; but in others, not above a line or two of it is 

 visible, till the belly of the insect be gently pressed. 

 When 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 chestnut- 

 brown color, and of a horny substance, a,nd 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 insect, in 



