13 HUMBLE CREATURES. 



for the Arachnidaej or spider tribes, are furnished with 

 eight ; the Crustacea, or crab-like races, usually with 

 ten ; and the Myriapoda, or millipedes, with an inde- 

 finite number of these members. 



With its six legs, constructed for progression on 

 terra firma or in the water, there are coupled, as a 

 general rule, one or two pairs of wings for flight in 

 the air : and we may here observe, that in order that 

 the body may be rendered lighter whilst moving in 

 this element, the insect races do not breathe, as we 

 do, by means of Inngs, but are provided internally with 

 numerous tubes and receptacles, of various dimen- 

 sions, termed tracheae, in which the air freely circu- 

 lates, diminishing the specific gravity of the trunk. 



Insects are furthermore rendered conspicuous by 

 their antennae or feelers, of which they possess a single 

 pair, situated in front of the head, and composed 

 of a series of rings or joints, in conformity with the 

 structure of the rest of the body. These feelers serve 

 to aid them in their numerous instinctive actions. 



Lastly, the insect races usually undergo a more or 

 less complete metamorphosis before arriving at the 

 perfect state. In some cases they pass from one 

 stage to the other without any marked change in 

 their external appearance ; in others, however, as in 

 the Bee, they are subjected to a complete transition 

 from the vermiform or worm-shaped grub or larva to 

 the winged insect or imago, and spend a portion of 

 their lives intermediate between these two stages in 

 a quiescent, and apparently a lifeless state, enclosed 



