Reproduction of Insects. 65 



In the female, the long terminal organs form the 

 ovipositor, or egg depositor. 



By means of this the female is able to conduct 

 the egg from the oviduct to a place suitable for its 

 development. She does not merely drop her egg 

 to find a lodging where it may, as the fish so often 

 does, but by means of the long tubular ovipositor 

 often places it in positions which without this 

 instrument would be totally inaccessible. 



The ovipositor assumes a great variety of forms 

 in the different species. 



Sometimes it is not a closed tube, but made of 

 separate grooved blades, which fit together to 

 form a tube when so needed. The blades may be 

 toothed like a saw, may be tipped with a sting 

 which connects with a poison sac, or may end in 

 a sharp point or drill, for boring holes in hard 

 substances ; in short, may be modified in an in- 

 credible number of ways. 



This ovipositor, this egg-conductor, is the fe- 

 male's priceless means of defence, and her imple- 

 ment for finding ingress into difficult, but for the 

 offspring, desirable, places. 



The saw-fly uses the toothed blades of the ovi- 

 positor to cut incisions in leaves and stems, where 

 it then deposits the eggs. 



The wound so made is, in some cases, accom- 

 panied by a secretion which irritates the plant 

 tissue, so that it grows up about the egg in the 

 form of a " gall," or little hollow chamber, in which 

 the egg cosily develops. 5 



