38 STUDIES IN AMERICAN TETTIGONIIDAE (oRTHOPTERA) 



tinctly breaking up, with the differentiation as yet visibly under 

 way, and of the elements monticola probably represents the great- 

 est divergence. The testaceus-pachijmerus line is more perma- 

 nent than the other line of the group, although the elements are 

 more divergent. The species pachymerus appears to be breaking 

 up at present. Group D is probably the oldest of the diver- 

 gences from the presumably ancestral line, and in dorsalis we may 

 assume we have the nearest to the primitive type of the group. 

 The species glaber and calcaratus form a relatively old Hne of 

 this group, but calcaratus is a much more specialized and differ- 

 entiated form than glaber. 



Notes on Male Tegmina. — The male tegmina are of use only 

 as stridulating organs and are largely or wholly covered by the 

 pronotum, the stridulating field proper being always covered, 

 the portion which is exposed caudad of the pronotum in most 

 of the species being the area distad of the speculum. The general 

 form of the speculum and surrounding veins and areas shows 

 some variation within specific limits, and again, in general char- 

 acter of the same, certain species show no important differences, 

 but as a whole the form of the stridulating field is a good group 

 character. The marginal field varies in form in certain closely 

 allied species (i. e. davisi and monticola). The coloration of the 

 tegmina is discussed under Coloration Notes. The tegmina of 

 the female are small, pad-like, always completely hidden under 

 the pronotum and of a general subcircular form. 



Morphological Notes on Male Genitalia. — The disto-dorsal 

 abdominal segment and the supra-anal plate of the male and of 

 the female show a considerable amount of variation in form. 

 The former is always emarginate mesad, but the same varies 

 from an obtuse-angulate to an arcuate character, and within 

 specific limits there is great variation in this respect. The 

 supra-anal plate is more or less trigonal in character, but a ten- 

 dency to become semi-elliptical is evident and this also is within 

 specific limits. The same plate bears, usually, a medio-lon- 

 gitudinal sulcus, which may be complete or may be apparent only 

 on the distal half. The cerci, as we have shown above under 

 Classification, develop four principal types, one in each group, 

 which are fairly or quite (gibhosus) decided and show no variation 

 from their specific forms except in the following ways. There 

 is a tendency to become more elongate or shorter and more 



