292 PTILOTA : IMAGO EXTERNAL ANATOMY. 



elongated abdomen ; as, for instance, the earwig, the Sta- 

 phyUnida, &c. Insects which, on the contrary, have the ab- 



Geerius olens. 



domen short, and especially those in which it is defended by 

 the wing-covers, possess but very little power of motion in 

 this part of the body. Another circumstance, also, has much 

 influence in the same respect , when the segments of the ab- 

 domen simply touch each other at the margins, the motion 

 is very limited; but in those which have the abdominal 

 rings formed to slide into each other, the motion is much 

 more extensive. 



The organs of generation (with the exception of those of 

 the male Libellulce, which have been considered to be placed 

 beneath the first abdominal segment) are situated at the 

 extremity of the abdomen. 



As the sexes of insects are distinct, and coupling requisite 

 for the continuance of the species, it is essential that the 

 males should be furnished with organs for the elaboration and 

 discharge of a fecundating fluid, and the females with organs 

 proper for its reception, for the developement of eggs, and 

 for the deposition of these eggs in the most convenient situa- 

 tions. The last-mentioned organs (which are by far the 

 most conspicuous of the generative organs) are of very varied 

 construction, the saws of the saw-fly, the long ovipositor 



