128 EVENINGS AT THE MICROSCOPE. 



for the deposition of the eggs, and is hence called an 

 ovipositor ■, though in many cases it performs a part much 

 more extensive than the mere placing of the ova. 



In the large tribe of Cuckoo-flies (Ichneumonidce) which 

 spend their egg- and larva-states in the living bodies of 

 other insects, this ovipositor is often of great length; even 

 many times longer than the rest of their bodies ; for the 

 larvae which have to be pierced by it require to be reached 

 at the bottom of deep holes, and other recesses, in whicli 

 the providence of the parent had placed them for security. 

 The structure of the organ may be seen in this little 

 species, not more than one-sixth of an inch in entire 

 length, of which the ovipositor projects about a line. 

 Under the microscope you see that this projection con- 

 sists of two black fleshy filaments, rounded without and 

 flattened on their inner faces, which are placed together, 

 and of the true implement for boring, in the form of a 

 perfectly straight awl, of a clear amber hue, very slender, 

 and brought to an abrupt oblique point, where there are 

 a few exceedingly fine reverted teeth. It is probably 

 double, though it refuses to open under the pressure 

 which I bring to bear upon it. At the base are seen 

 Avithin the semi-pellucid abdomen the slender horns, on 

 which the muscles act in projecting the borer. 



You are doubtless aware that the little berries which 



GALL-FLY, AND MECHANISM OF OVIPOSITOR. 



look like bunches of green currants, often seen growing on 



