176 INVERTEBRATE ANIMALS. 
present, and the améerzor pair is quite rudimentary, and is only 
represented by curious twisted filaments, from which the name 
of the order is derived. 
ORDER XII. COLEOPTERA.—The twelfth and last order of 
insects is that of the Coleoptera, including the well-known 
insects familiar to every one under the name of “ beetles.” 
The leading peculiarity of the Coleoptera is to be found in 
the fact, that though all the four wings are present, only the 
posterior pair are membranous, and perform the function of 
wings. The anterior pair of wings (figs. 91, 92), are no longer 
capable of being used in flight, but are hardened by the deposi- 
Fig. 91.—Coleoptera. @ Rose-chafer (Cetonza aurata) and larva ; 
b Vine-weevil (Curculio sulcatus). 
tion of chitine, and constitute protective cases, which cover the 
hind-wings, and are known as “elytra” (Gr. e/utron, a sheath). 
The mouth in all the beetles is masticatory, and is furnished 
with biting and chewing jaws. 
The larvee of the beetles are all worm-like grubs, with mas- 
ticatory mouths, and they all pass through a complete meta- 
morphosis, generally requiring a protracted period for its 
completion. The known number of different kinds of beetles 
cannot be estimated with any certainty, but it is probably little 
short of 50,000 species, and this estimate has been doubled by 
