August — December 1SS9.] 



PSYCHE. 



271 



cations than parts which are confined to 

 or are more perfectly developed in fe- 

 males." 



On this point it will be sufficient to 

 call to mind that the organ which is al- 

 most entirely restricted to the males of 

 locustidae., gryllidae.^ and acrididae is 

 the musical apparatus. In acrididae 

 this apparatus is too little specialized to 

 repay examination. In locustidae and 

 gryllidae there is little evidence to be 

 found of an unmistakable character, but 

 the last mentioned family has one genus 

 Oecanthiis and the first mentioned two 

 genera Couoccpiialits and OrcheliiniiDi 

 which throw some light on the subject. 

 Concerning Oecanthus I may say 

 that the three most common species 

 are niveiis^ De Geer, angnstipeiiftis^ 

 Fitch, and fasciatus Fitch. These 

 species are usually considered to be 

 mere varieties, and although I am satis- 

 fed tiiat the distinctions of form and 

 habits and to a less degree of color en- 

 title them to rank as species, their 

 very distinct "songs" leave scarcely any 

 room for doubt. Of course this difter- 

 ence in the character of stridulation is 

 accompanied by a certain, though not 

 conspicuous, difference in the structure 

 of the stridulating appai'atus, and bv its 

 tending to vary in structure and use, 

 it aids greatly in establishing two spe- 

 cies. In Conocepkaliis and 0>-cheIiiii?/jn 

 the evidence is similar. The species for 

 the most part are vei'y similar and the 

 most certain means of distinguishing 

 tliem is in their songs. 



3. ''That a part which is confined to 

 or is most developed in males is more 



likely than a similar female part to 

 vary." 



This principle is well illustrated in 

 the anal cerci of the males of Melaiio- 

 plus., Pezotettix^ and Acridinm. 



This part which has been before 

 remarked in the females is simple and 

 constant in form, in the males is ex- 

 tremely variable in size and shape, so 

 that in the two genera first mentioned, 

 at least, it furnishes the best specific 

 characters for distinguishing the species. 

 In these genera also the males furnish 

 good specific characters in the form of 

 the last ventral segment, while in the 

 female this part is very constant in form. 



4. " rhat males are, as a rule — more 

 variable than females." 



Much of the evidence already given 

 bears upon this point — and I will con- 

 tent m\self with a verv few more 

 examples. 



The males of two species of Tridacty- 

 lus, T. apicalis Sav and T. tcr/niiialis 

 Uhler have the anterior tibiae furnished 

 with a very remarkable appendage. 



The tibiae are divided into two forks 

 nearly at right angles to each other. 

 That fork which occupies the usual posi- 

 tion of the tibiae ends in two strong 

 spines. From its base the true tibia 

 extends backward parallel with the 

 thigh, with wdiich it forms a raptorial 

 apparatus. This brand ends in a strong 

 curved claw — and a very diminutive 

 tarsus which is placed at right angles 

 to the tibiae. In these species the 

 males are further distinguished from the 

 females by the swollen pronotum. 



In the genera CentJiophihis and 



