ORDERS OF INSECTS. 



181 



only represented by curious twisted filaments, from which the name 

 of the order is derived. 



Order XIII. 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. 127, 128) are no longer 

 capable of being used in flight, but are hardened by the deposition 

 of chitine, and constitute protective cases, which cover the hind- 

 wings, and are known as "elytra" (Gr. elutron, a sheath). The 

 mouth in all the Beetles is masticatory, and is furnished with biting 

 and chewing jaws (fig. 109, A). 



The larvae of the Beetles are all worm-like grubs, with masticatory 

 mouths, and they all pass through a complete metamorphosis, gen- 

 erally requiring a protracted period for its completion. The known 



Fig. 127. — Coleoptera. A, Cicindela campestris, the 

 Tiger - beetle, enlarged. B, Larva of the same, 

 enlarged. C, Dytiscus marginalis, male. 



Pig. 128.— a, Rcse-chafer 

 (Cetonia aurata) and 

 larva. 



number of different kinds of Beetles cannot be estimated with any 

 certainty, but it may be safely said that the order is one of the 

 largest of all the groups of Insects. They are, as a general rule, 

 remarkable for their hard chitinous skin, their glittering, often 

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