BEETLES. 307 



a vngina, that ojiens into a inorc or less extensile ovipositor. The hiirsa eopulatrix 

 and reeejitaeiiluin seminis are generally present as accessory organs of the vagina. The 

 male sexual organs consist of from one to six testes on each side, opening into a vas 

 deferens, the two vasa <leferentia usually expand to form a pair of vesiculre seminales, 

 and then, receiving ducts from accessory glands, unite, to form a conunon efferent 

 canal into the extensible penis. 



The e<i'<i's are covered with an egt^'-shell or chorion which is generally not verv tirm, 

 and are rarely, as in the case of a water-beetle {I/i/drojj/tilus), deposited in a nest. A 

 few beetles are vivij)arous, among them certain rove-beetles (Staphylinid*) and the 

 Stylopida^ One species of cln-ysomelid (Gastroj)hi/sa ruphani) has been shown by 

 J. A. Osljorne to be capable of parthenogenetic reproduction. Apparent hermaphro- 

 dites rarely occur as monstrosities wherein some secondary sexual character of one sex 

 is borne by an individual of the opposite sex, lint no real case of hermaphroditic Cole- 

 optera is known. Cojiulation sometimes takes place between different species of a 

 genus, and less commonly between sj)ecies of different genera. 



Tlie muscular system needs no special descri]ition. The Coleoptera are among the 

 strongest of insects, and Professor F. Plateau found that the common Enrojiean dor- 

 bug (^Melolo)itha vuhjaris) could exert a traction along a horizontal surface equal to 

 forty times its own weight. 



The sense organs are necessarily ])artly external and partly internal, that is they 

 are made up of moditied external parts to receive impressions, and nerves connecting 

 these parts with tiie central nervous system. The olfactory organs, as already mentioned, 

 are in the antenna;, and by their aid dung-beetles are guided long distances to their 

 food, and certain other beetles to their mates of the other sex. Eyes and ocelli are 

 the organs of sight. The location of the auditory organs has not been determined 

 with certainty, but lieetles surely hear, because they are often provided with sonoritic 

 organs. The sense of touch is especially developed in tlie antetnue, paljii and tarsi, 

 where the tine hairs communicate with nerves at their liases. The organ of taste has 

 not been certaiulv loi'ated, but possibly in beetles it is upon tlie hyjiopharynx, an ex- 

 tension of the pharvngeal walls just above the labium. 



Allusion has just been made to the fact that beetles often produce more or less 

 musical sounds — stridulate as it is termed by entomologists. This stridulation is 

 produced bv nibbing different jiarts of the body, wings, or legs against each other, and 

 is observed very commonly among the longicorns (Ccrambycida'). If one of the red 

 and black beetk'S with long antenna' (species of 7''etraopes), that are so abundant on 

 different kinds of milk-weed (Axc/fpias) during the latter part of sumnu'r and during 

 autumn, be pinned, in the usual way, upon the cip\er of a cigar-box, or u])on anything 

 else that serves as a sounding-board, the stridulation can be demonstrated to a consid- 

 erable audience. By jn-essiiig from lime to time njion the tij) of the elytra of the 

 Tetraopes the sounds will be renewed vigorously at the will of the experimenter, and 

 the protliorax of the beetle will be seen to bend rapidly forwanl and backwards. 

 The sound is ])rodnced l>y the rulibing of a sharp angular ridge upon the prothorax 

 against a finely striated surface on the metathorax, a mode of sonifaction on a small 

 scale similar to that where a Iioy runs along a fence ]iuslun^* stick against tlie pickets. 

 H. Landois, who studied sound ]ivoduclnon by insects, asserts that all Ccrambycida? 

 large and small species alike, are provided with stridulating ap|iaratus, whether one 

 hears their tones or not, and he draws from this fact the conclusion that beetles pro- 

 duce sounds beyond the reach of the human car. In the grave-digger (X^(croj>/iorus) 



