CHAPTER XXIII 

 ORDER COLEOPTERA* 



The Beetles 



The winged members of this order have Jour wings; hut the first pair 

 of wings are greatly thickened, forming a pair of "wing-covers" or 

 elytra, beneath which the membranous hind wings are folded when at rest. 

 The elytra meet in a straight line along the middle of the back and serve 

 as armor, protecting that part of the body which they cover. The mouth- 

 parts are formed for chewing. The metamorphosis is complete. 



The order Coleoptera includes only the beetles. These insects can 

 be readily distinguished from all others except the earwigs by the 

 structureof the fore wings, these being homy, 

 veinless "wing-covers" or elytra, which meet 

 in a straight line along the middle of the 

 back (Fig. 544); and they differ from ear- 

 wigs in lacking pincer-like appendages at 

 the caudal end of the body. Beetles also 

 differ from earwigs in having a complete 

 metamorphosis. 



Only a few modifications of the t^^pical 

 characteristics exist in this order; among the 

 Fig. ^^^.—Desmocerus pal- ^lo^e familiar of these are the following : in 

 liatus. some of the Meloidae the elytra do not meet 



in a straight line ; in many of the Carabidse, 

 Curculionidse, et al., the hind wings are wanting, and in some of these 

 the elytra are grown together; in a few females of theLampyridasand 

 Phengodidas both pairs of wings are wanting. 



The different mouth -parts are very evenly developed; we do not 

 find some of them greatly enlarged at the expense of others, as in 

 several other orders of insects. The upper lip, or labrum, is usually 

 distinct; the mandibles are powerful jaws fitted either for seizing 

 prey or for gnawing; the maxillae are also well developed and are 

 quite complicated, consisting of several distinct pieces; the maxillary 

 palpi are usually prominent; and the lower lip, or labium, is also well 

 developed and complicated, consisting of several parts and bearing 

 prominent labial palpi. Detailed figures of the maxilla and labium 

 of beetles are given in Chapter II. 



In the classification of beetles much use is being made of the 

 variations in form of the ventral and lateral sclerites of the thorax. 

 Figure 545 will serve as an illustration of these sclerites. One feature 

 merits special mention: the coxae of the hind legs are flattened and 

 immovably attached to the thorax so that they appear to be a part 

 of the thorax instead of the basal segment of an appendage. 



Coleoptera: coleos (KoXeds), a sheath; pteron {irrepby), a wing. 



(464) 



