294 PEOCEEDINGS OF THE ACADEMY OF [May, 



The genus Gryllus is found in America everywhere from southern 

 Canada to Patagonia. Many forms are developed, distinctive in 

 appearance to different degrees, but possessing in not a single instance 

 valid and constant specific characters, with the exception of Gryllus 

 domesticus, a distinctive introduced species. 



The different manifestations of the only native American species, 

 Gryllus assimilis, are in no case sufficiently differentiated or constant 

 to be considered geographic races. They constitute mere variations, 

 the adaptation of this exceedingly plastic species to local environ- 

 mental conditions. All are in varying degrees unstable./ but certain 

 geographic limits naturally bound the distribution of each, thus 

 desert adaptations, such as those described as personatus and armatus, 

 are never found in the well watered portions of the continent, nor is 

 the tropical adaptation, assimilis, found in the extreme northern 

 or southern portions of the range of the species. This is of course 

 explained by the fact that the environmental conditions producing 

 these variants are not found over portions of the range of the species. 



The work of Lutz- has already demonstrated the error of using 

 length of tegmina, wings and ovipositor as characters of specific 

 importance in the genus Gryllus. The mass of evidence upon these 

 features in Lutz's paper is absolutely convincing; from studies of 

 other genera we have found such characters to be of minor importance 

 generally throughout the Orthoptera. Finding no other characters 

 which could Avarrant specific distinctions in the mass of American 

 material which he carefully bred and studied, Lutz has, however, 

 stated that all the forms of Gryllus are conspecific. His examination 

 of the series of females of the genus in the British Museum should 

 have shown him the error of this opinion, but he apparently con- 

 fined his studies to the variations in organs of flight and ovipositor,^ 



^ Of these, the personatus variant, showing the maximum condition of desert 

 adaptation, constitutes the nearest approach to a geographic racial development. 

 No intergradation is to be found with the more northern variants or with the 

 other desert adaptation, armatus, found also in the arid regions of the south- 

 western United "States, which latter appears to be derived from the northern 

 variants, various conditions of which are found in the higher mountains every- 

 where in the region under consideration. The personatus variant, however, 

 normally very pale in general coloration, is found to be occasionally much darker, 

 and from along the Mexican border such specimens are before us showing the 

 traiisition to, and the tjqaical condition of, the mexicanus variant. 



^ The Variation and Correlations of Certain Taxonomic Characters of Gryllus, 

 pp. 1 to 63 (1908.) 



^ In length of ovipositor, however variable, different extremes are found for 

 each distinct species. For many species these differences may be negligible, 

 but for some species the maximum and minimum are very different. Such features, 

 however, can only be accm'ately ascertained after specific units have been located 

 through the use of definite valid specific characters. Thus, in the study of females 



