90 



ABDOMEN OF INSECTS, AND ITS APPENDAGES. 



replaced by two small moveable threads, thickened at the end, 

 which are called balancers (Fig. 405). 



666. The abdomen of Insects is composed of a considerable 

 number of rings, moveable upon each other ; we can frequently 

 reckon nine of these ; but at other times we cannot distinguish 

 so many ; this appears to depend on the union of two or more 

 of these segments with each other. In the perfect Insect, these 

 rings never bear any legs or wings ; but those which occupy the 

 posterior extremity of the body, often give attachment to ap- 

 pendages, whose forms and uses vary very much. Sometimes 

 they are simple bristles, or points, whose functions are not well 

 known ; as in the Ephemera (Fig. 434) for example. Sometimes 



these organs possess the form of hooks ; and 

 constitute a more or less powerful pair of pin- 

 cers, as amongst the Forficulce, or Earwigs 

 (Fig. 406). At other times they are so 

 arranged, as to act as a spring, and to enable 

 the animal to throw itself forwards ; the 

 Podurce, or Spring-tails, small insects, which, 

 in our climate, conceal themselves under 

 stones, or keep themselves on the surface of * 

 still water, and which also live sometimes in 

 the snow of the coldest regions of the globe, 

 show this mode of organisation. 



667. In other instances, the abdomen bears appendages of a 

 more complicated structure, con- 

 stituting an offensive weapon, or 



an apparatus destined to effect 



the deposition of the eggs laid by 



the animal in a place fitted for 



the development of its young ; 



as examples of these organs, we 



may mention the retractile sting 



of the Wasps and Bees, and the piercer of the Tenthredos, or 



Saw-flies, The former is composed of a dart, formed of a 



horny spike channelled throughout its whole length beneath, 



and of two thinner filaments which are received into the furrow 



of the first piece so as to close it beneath and form a tube or cam 



FIG'. 406. FORFICULA. 



FIG. 407. Pommx. 





