STRUCTURES OF EARWIGS. 43 



straight line down the back, are without veins and cover only a 

 portion of the abdomen. The inner wings, when present, are 

 usually very large, rounded, and bear numerous radiating veins 

 which act like the bars of a fan in folding and unfolding the 

 wings. When at rest, these wings are folded both lengthwise and 

 crosswise beneath the protecting tegmina. They vary much in 

 size and development even in the same species, and Burr (1910, 

 451) has well said that "the abbreviation of the wings is a very 

 common character among earwigs and is absolutely valueless as 

 a specific character, although it somewhat alters the superficial 

 appearance of the specimens." The abdomen ends in a pair of 

 appendages which somewhat resemble forceps, whence the family 

 name Forficulida\ These doubtless represent the cerci of other 

 suborders of Orthoptera, and vary much in shape according to 

 species but are always more simple in the female than in the op- 

 posite sex. Were it not for these appendages the earwigs would 

 resemble very closely some of the Staphylinida* or rove beetles of 

 the order Coleoptera, the semblance being increased by most spe- 

 cies of each group curving the abdomen upward when disturbed. 

 Those species which possess inner wings use the forceps to aid in 

 folding these organs after flight, and they perhaps also aid to 

 some extent as clasping organs during the mating of the sexes. 

 The legs are of nearly equal size, the hind femora not enlarged ; 

 tarsi never more than three-jointed and usually without pads be- 

 tween the claws. No organs for producing sound are present, 

 and as far as known hearing organs are also absent. The sexes 

 are distinguished by the structure of the forceps, or by the num- 

 ber of ventral segments in the abdomen, there being eight in the 

 male and six in the female. In some tropical species the forceps 

 are longer than the abdomen, while in others they are noted for 

 the variety of their teeth and curves. 



Certain earwigs possess what are known as "foetid glands," 

 which open at the hind margins of the dorsal plates of the second 

 and third abdominal segments. From these they can squirt forth 

 to a distance of three or four inches a yellowish-brown liquid or 

 emulsion, having the odor of a mixture of carbolic acid and creo- 

 sote. This is used for defense as a repellant against their 

 enemies. 



Latreille (1831) states that: "The digestive canal of an ear- 

 wig consists of an oesophagus, a large elongated crop, and a short 

 gizzard furnished internally for trituration with six ridges in the 



