438 The University Science Bulletin. 



from Kansas. The problem was undertaken with no preconceived 

 notions in the matter, except, indeed, a leaning toward accepting 

 Doctor Montandon's studies, since he is a great scholar in the 

 Cryptocerata and was followed by Van Duzee in his catalogue. The 

 results herewith presented may be received with some irritation, 

 because of the revolution necessary in nomenclature, but it seems 

 best for us to get as near the truth as the evidence permits. 



In an endeavor to fix the limits of the species, the writer has 

 studied the characters used by the best systematists in the group 

 and in addition, antennal and genital structures. The relative length 

 of body parts, the comparative size of the eyes, the relative length 

 of the limbs and of the caudal filaments, the shape of the sternum 

 and the form of the front femora have been in general use in the at- 

 tempts to define nature's species in this genus. Species are expected 

 to vary within limits, and breeding experiments with insects show 

 them to vary, not only in single characters, but in linked characters, 

 and in order to steer a fair course between ''lumping" and ''split- 

 ting" species, it is much better to use a combination of three or more 

 characters than to depend too much upon any single one. The use, 

 therefore, of the characters of the antennae and genitalia is a ma- 

 terial aid in the classification of this difficult group. 



NOTES ON TERMS USED IN KEYS AND DESCRIPTIONS. 



The apical tooth of the front femur is on the inside edge of the 

 front femur near the attachment of the tibia (see fig. 2-A, pi. 

 XLIV). The antennae are hidden in pockets beneath the eyes (see 

 fig. 9^ pi. XLV). The prothorax of Ranatra is divided into two 

 parts, anterior and posterior, by transverse lateral grooves (see fig. 

 2-G, pi. XLIV). The tylus and jugae are figured on plate XLV, 

 figure 12. The metaxyphus extends back between the hind coxae 

 as a part of the metasternum. The last abdominal segment is desig- 

 nated as the "genital segment," and its ventral plate in both sexes as 

 the "operculum." 



In this paper I have not distinguished between the genital seg- 

 ment and the last abdominal segment, as is often done with some 

 other Heteroptera, where the last abdominal segment is considered, 

 the segment just in front of the genital segment. I refer to this as 

 the penultimate abdominal segment (see figs. 10 and 11, pi. XLV). 



The male genital capsule of which I speak is, I take it, homolo- 

 gous with what G. C. Crampton in the Bulletin of the Brooklyn 

 Entomological Society, volume XVII, pages 45-55, calls the hypan- 

 drium," and the claspers correspond to his "styli," or "gonostyles." 



