4 OKTHOPTERA. 



those incident to wide distribution, with its concomitant differences in environment, we 

 have presented an amount of difficulty before which the most experienced systematist 

 may reasonably pause. Notwithstanding, it is a most interesting assemblage— containing 

 many graceful, grotesque, dainty, bizarre, and beautiful forms, as a glance at the pages 

 of Bolivar's monograph will show — and offers to the student of variation, of evolution 

 of form, a field where he will be put upon his mettle. 



A point has been reached, in some genera at least, where the methods of study and 

 publication hitherto in vogue must give way to something better, more thorough and 

 scientific : material must be secured in sufficient series and from particular localities ; 

 descriptions, however minute and carefully worded, must be accompanied by drawings 

 of details known or likely to be of diagnostic value, in order to convey a sufficiently 

 definite knowledge of the form described. This plan, which I had hoped to follow in 

 the present treatise, I have reluctantly been compelled to abandon. Nor can I hope 

 to have been more uniformly successful in the discrimination of species than my 

 predecessors. 



The sequence of groups and genera is that adopted by Bolivar in his scholarly 

 ' Essai ' *, a work that is a necessity to the student of the subfamily. The keys to 

 genera and species are based upon this, though I have discarded certain characters 

 which experience has shown to be misleading or of little importance — notably that of 

 difference in extent of pronotum and wings, a kind of dimorphism of very common 

 occurrence in the -entire family. 



The most useful characters of practical value are those drawn from the form and 

 proportions of the eyes, vertex, and facial costa ; the form of the pronotum and its 

 parts (exclusive of mere length) ; of the femora, especially the intermediate ; and, to 

 some extent, the proportionate length of the joints of the posterior tarsi. I have also 

 made some use (e.g. in Tettigidea) of a character not hitherto reported which should 

 be explained here. If a sufficient number of Tettiginae be examined, it will be noticed 

 that opposite the distal end of the tegmina the lateral carinas run obliquely downward 

 and backward from the dorsal edge of the disk of the pronotum to the ventral edge of 

 the hind process. Behind this point the dorsal edge of the process is usually formed 

 by a carina which generally is continued forward a greater or less distance nearly 

 parallel to the lateral carina, sometimes not disappearing until after it has crossed the 

 shoulder, and separating in such cases a narrow triangular or linear area from the rest 

 of the disk. This carina I have called the humero-apical carina, and the area cut off 

 by it the scapular area (see figures of Otumba and Tettigidea). Under measurements, 

 " total length " refers to the distance from the vertex to the end of the pronotum or 

 wings as the case may be. 



Besides Bolivar's ' Essai,' the only work worthy of note in connection with the region 



* Bolivar, Ign., " Essai sur les Acridiens de la Tribu des Tettigidae " [Annales de la Societe Entomologique 

 de Belgique, xxxi. pp. 175-313, tabb. 4, 5 (1887)]. 



