66 



PROCEEDINGS OF THE ACADEMY OF 



[Jan., 



relative size and width of space between the tegmina, 'form of the 

 ovipositor and that of the subgenital plate. The general form is 

 much more robust in some species than in others, the females almost 

 always more robust than the males, in falcata and poUicifera less 

 different in this respect than in the other forms. The outline of the 

 eye is, in a few cases, of assistance in distinguishing females of closely 

 allied forms, as castanea and brevihastata. The pronotum ranges 

 from not at all constricted, to decidedly constricted mesad in both 

 sexes. In the male sex the tegmina show modifications in the form 

 of the margins and the width of the fields, the prominence of the 

 stridulating vein and the projection of the sutural margin at the apex 

 of the same vein. The tegmina of the female are as diagnostic as 

 the more complex appendages of the male, their relative position and 

 the interspace between the same, as well as the form of their margins, 

 being of importance. The characters of the genitalia of the two sexes 

 are discussed in detail below. 



Morphological Notes on Male Genitalia. — The variation in struc- 

 tural form in the cerci of the male covers a number of types which 

 show six different lines of development, relatively as follows: 



(mexicana 

 falcata 



durangensis 



D 



{castanea 

 brevihastata 



( gladiator 

 { emarginata 



(oreoeca 

 catinata 



F- 



( caudelli 



\ 



tridactyla 



E — taurijormis 



C — poUicifera 



B — serrifera 



The position of durangensis is more or less problematical, as we have 

 only nymi)hal males. 



