BEETLES. 305 



which enable the tip of the wing to fold back, in one or sometimes more folds, with- 

 out too greatly weakening its structure, are an interesting study. If one pulls open 

 forcibly the wing of a large water-beetle (Dytiscus) that has been preserved in alco- 

 hol, the wing will partly close itself by its own elasticity, and such a wing furnishes 

 an excellent object on which to study the folding mechanism. 



A few beetles are wingless and cannot fly ; their elytra are united to each other on 

 the inner side, and they are said to have connate elytra. In such cases the original 

 function of the elytra and wings, that of flight, has been superseded by a secondary 

 function of the elytra, protection. Rarely both elytra and wings are absent, as in the 

 females of certain "lightning-bugs" (Lampyridse), which are thus rendered so worm- 

 like that they are called popularly " glow-worms." 



The flight of beetles is generally heavy and slow ; some, however, can fly very 

 quickly, but most rapid-flying beetles rest often from flight, and can be chased down 

 and captured without great difficulty in an open field. A sport which children enjoy 

 is chasing down, in this manner, the tiger-beetles (Cicindelidse). 



While the genitalia of most beetles are concealed in the abdominal segments, 

 secondary sexual characters are so manifest in many species as to attract the atten- 

 tion even of careless observers. As already mentioned, the anterior tarsi of some 

 beetles serve to distinguish the males from the females ; in a few water-beetles (Dytis- 

 cidae) fluted elytra are found in some females, while the elytra of other females of the 

 same species are not fluted truly dimorphic females ; in many Scaraba3idae, in some 

 Cerambycidas, and in many other Coleoptera, the males have larger and better devel- 

 oped antennas than the females have ; a large number of Scarabasidas and a few other 

 beetles have, in the male, well-developed horns upon the prothorax, or upon the head, 

 or upon both head and prothorax, while their females have no horns, or much less 

 developed ones in the corresponding positions ; in the stag-beetles (Lucanidas) the 

 mandibles of the males are excessively developed. The sex of beetles is sometimes 

 determinable in the pupal state from their evaginated or protruded genitalia. 



Beetles, or their parts, may be smooth, striate, punctate, cancellate, or may have 

 many other modifications of surface. They may be clothed with waxy secretions, 

 spines, hairs, or even scales. The excessive brilliancy and sparkling coloration of the 

 so-called diamond-beetle of Brazil (Entimus imperialis, of the Curculionidaa), which 

 will be figured further on, is due to its being covered with scales : this kind of orna- 

 mentation with scales really only modified hairs is common among the weevils 

 (Curculionidas), and not rare in a few other families of Coleoptera. Beetles exhibit 

 almost every known shade of color, and a few are iridescent with beautiful metallic 

 hues. A little beetle ( Coptocyda aurichalcea) not uncommon on the wild morning- 

 glory (Convolvulus), looks, when alive, like a flattened drop of the finest polished 

 gold. The species of certain families resemble one another in coloration and figura- 

 tion ; the leaf -beetles (Chrysomelidae) have, for the most part, brilliant coloration ; 

 the lady-birds (Coccinellidre) have for prevailing colors red, yellow, and black, mostly 

 arranged in round or roundish spots ; the Tenebrionidas are generally sombre colored, 

 often dull black. 



The internal anatomy of Coleoptera is not as varied as is that of many other insects, 

 and the main facts can be condensed, in a general way, to the following statements. 



A narrow oesophagus, into which often open salivary glands, passes into a crop, 

 the posterior portion of which is lined, in carnivorous Coleoptera, with chitinous teeth, 

 serving as a gizzard. Behind the gizzard the digestive tract, which has a few convolu- 



VOL. II. 20 



