50 



OUTLINES OF ENTOMOLOGY. 



CHAPTER XIV. 

 Order 11. coleoptera. 



[Fig. 22.] 



A Carabid, Calosoma calidfum with larva 

 (after Riley)'. 



This Order of insects — the Beetles — includes a far greater number 

 of described species — more than one hundred thousand — than either 

 of the other primary groups. And while among this vast assemblage 

 we find an almost infinite variety in size, form, color and the adaptation 

 of certain organs for certain functions, a single glance is suflBcient to 

 enable us to recognize a member of the Order, except, perhaps, in 

 the case of a very few rare and unusual forms. 



On account of the ease with which specimens may be collected and 

 preserved, and the accuracy with which the external structure may be 

 defined, these insects have always been favorites with entomologists, 

 and the student will find them most interesting and convenient subjects 

 upon which to begin his studies of insect anatomy. 



The popular term "beetle" is said to be derived from an old Eng- 

 lish word signifying a "biter," and is most appropriate tor this groui> 

 of insects in which the organs for biting are so complex and so perfect. 



Beetles are chiefly characterized by the peculiar structure of the 

 upper wings, which are transformed into a pair of horny or leathery 

 cases, or sheaths meeting in a straight line down the back, and covering 

 not only the abdomen, but two joints of the thorax (the mezo and meta 

 thorax). These are called the elytra (sing, elytron). They are not used 

 to any extent in flight— their otfice appearing to be mainly that of armor 

 for the protection of the softer parts of the body. The true membran- 

 ous wings, when not in use, are snugly folded beneath them, not only 

 lengthwise, in fan-like plaits, but, by means of a hinge or joint in the 

 supporting veins, a little beyond the middle, crosswise as well, so that 



