164 



AN ECONOMIC ENTOMOLOGY. 



CHAPTER VI. 



THE COLEOPTERA OR BEETLES. 



Fig. 126. 



The Coleoptera, ' ' horn-winged' ' insects, or beetles, are dis- 

 tinguished by the hard, horny, or tough, leathery texture of the 

 fore-wings or elytra, which meet in a straight line down the 

 middle of the back, and are not used in flight, serving as wing- 

 covers only. They vary greatly, and are numerous in specimens 

 and species, over twelve thousand kinds having been described 

 from the United States and British America alone. They are as 

 diverse in habit as in size and form, some being among the most 

 dangerous enemies of agriculture, while others are among the 

 most useful. 



It seems at first sight as if the recognition of beneficial or in- 

 jurious forms among so many would prove a hopeless task, and 

 yet we find it in most cases possible to say at a glance whether a 

 given specimen is herbivorous, i.e., plant- 

 feeding, or carnivorous, i.e., flesh-feeding 

 and predaceous. 



All beetles are mandibulate and chew their 

 food ; but in one series the head is more or 

 less prolonged into a snout or beak, at the 

 end of which the much reduced mouth parts 

 are situated. These are the Rhynchophora, 

 or "snout-beetles," all of which are plant- 

 feeders and injurious, or likely to prove so. 



The true Coleoptera, in which the head is 

 not prolonged into a beak, we can separate 

 by the structure of the tarsi or feet. Nor- 

 mally there are five joints or segments to 

 each pair of feet ; but there are many de- 

 partures from this rule, one large series having four apparent 

 joints only, of which the third is lobed or deeply notched. The 

 species in which this structure obtains are all plant-feeders ; 

 either on leaves or in stems, trunks, branches, or roots ; often 

 in dead, though more usually in living tissue. In no other case 



Tarsi in Coleoptera.— 

 c, normally five-jointed ; 



b, normally four-jointed ; 



c, four-jointed, with the 

 third joint deeply lobed, 

 from side and from above. 



