BEETLES. 307 



a vagina, that opens into a more or less extensile ovipositor. The bursa copulatrix 

 and receptaculum 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 deferentia usually expand to form a pair of vesiculoe seminales, 

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

 canal into the extensible penis. 



The eggs are covered with an egg-shell or chorion which is generally not very firm, 

 and are rarely, as in the case of a water-beetle (Hydrophilus\ deposited in a nest. A 

 few beetles are viviparous, among them certain rove-beetles (Staphylinidae) and the 

 Stylopidae. One species of chrysomelid ( G-astrophysa raphani) has been shown by 

 J. A. Osborne 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, but no real case of hermaphroditic Cole- 

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

 genus, and less commonly between species of different genera. 



The muscular system needs no special description. The Coleoptera are among the 

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

 bug (Melolontha vidgaris) could exert a traction along a horizontal surface equal to 

 forty times its own weight. 



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

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

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

 are in the antennas, 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 beetles surely hear, because they are often provided with sonorific 

 organs. The sense of touch is especially developed in the antenna?, palpi and tarsi, 

 where the fine hairs communicate with nerves at their bases. The organ of taste has 

 not been certainly located, but possibly in beetles it is upon the hypopharyux, an ex- 

 tension of the pharyngeal 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 by rubbing different parts of the body, wings, or legs against each other, and 

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

 and black beetles with long antennas (species of Tetraopes), that are so abundant on 

 different kinds of milk-weed (Asclepias) during the latter part of summer and during 

 autumn, be pinned, in the usual way, upon the cover of a cigar-box, or upon anything 

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

 erable audience. By pressing from time to time upon the tip of the elytra of the 

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

 the prothorax of the beetle will be seen to bend rapidly forward and backwards. 

 The sound is produced by the rubbing 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 boy runs along a fence pushing a stick against the pickets. 

 H. Landois, who studied sound production by insects, asserts that all Cerambycida> ? 

 large and small species alike, are provided with stridulating apparatus, 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 ear. In the grave-digger (Necrophorus) 



