432 Transactions. 



upon by birds ; and even if it did repel certain potential enemies, such 

 special means of protection would be far more necessary for tbe preser- 

 vation of the female whilst depositing her eggs than it would be for the 

 male. 



2. Order Orthoptera. 



In the small order Orthoptera, which includes the wetas, grasshoppers, 

 crickets, walking-sticks, and allied insects, we have several striking instances 

 of the operation of sexual selection. 



The Stenapelmatidae, or wetas, were long supposed to be destitute of 

 sound-producing organs, although possessing an auditory organ on each 

 of the tibiae of the anterior pair of legs. A careful examination of the 

 side of the second abdominal segment of both sexes, however, reveals the 

 presence of about six minute file-like organs, which are operated upon by 

 the inner edge of the base of the femur of the hind legs, these legs being 

 raised above the insect's back when it is stridulating. By this means the 

 weta can produce a harsh grating sound, which is employed to intimidate 

 enemies and also possibly as a call or lure to the female. This stridulation 

 of the weta may often be heard in the bush at night. 



In the males of the true grasshoppers with short antennae (Acridiidae) 

 a long file-like structure is situated on the inner side of the thigh of the 

 hind leg, and the sound produced is used to attract the female. 



In addition to the stridulating-apparatus, the male of our commonest 

 weta (Deinacnda megacephala) has a huge head and jaws, the corresponding 

 parts in the female being of the ordinary size. These males are sometimes 

 found in holes in trees and similar situations, and are often accompanied by 

 several females, the proportion of the sexes in this particular species being 

 about one male to three females. As wetas come abroad only at night, 

 it is difficult to obtain much precise information regarding their habits ; 

 but I think there can be little doubt that a very keen rivalry must exist 

 between thQ males, and the great head and formidable jaws have been 

 acquired as the result of this rivalry, the most ferocious, powerful, and 

 * well-equipped males having alone succeeded in leaving descendants. Apart 

 from theoretical considerations, the preponderance in the number of 

 females, the reverse proportion to that usually subsisting amongst insects, 

 is strong presumptive evidence that a large proportion of males must 

 perish, and the only conceivable means by which this unusual disparity 

 in the numbers of the sexes could be brought about is through the 

 destruction of the weaker individual males during their contests to possess 

 the females. 



In the Locustidae, or long-horned grasshoppers, a vein on one of the 

 wing-cases of the male is furnished with minute ridges, and the sound is 

 produced by the insect rubbing this against a raised vein on the other 

 wing-case. Coedicia oUvacea, a beautiful leaf-like insect occurring in 

 Australia, which to my knowledge has been common round Nelson for 

 thirty-five years, is an excellent example of this family. In the autumn 

 evenings its chirj)ing may often be heard in all directions. 



In. the true crickets (Gryllidae) both wing-cases bear file-like organs 

 which are rasped together by the insect and thus produce the well-known 

 chirping. Our example of /this family is the black Australian cricket 

 (Gryllus servillei), which is also Yerj abundant in the Nelson Province, and 

 its stridulation is a most familiar sound on fine summer evenings. 



Referring to the diversity of these special soimd-producing organs in 

 the males of the Orthoptera (crickets and grasshoppers) and the Hemiptera- 



