INVESTIGATIONS ON THE MUTILLID WASPS 41 



ficially very much alike. It has been possible to determine that 

 certain external characters were of specific value by using the geni- 

 talia as a criterion. On the other hand certain groups of males 

 quite different in superficial appearance possess genitalia which are 

 practically identical, so that these structures have been of assistance 

 not only in the distinguishing of species, but also in determining the 

 relationships of species, which is exceedingly important from the 

 viewpoint of phylogeny. 



Figures of the genitalia have been drawn and are reproduced here- 

 with on the following scale : 1 mm. in the drawing equals 0.039 mm. 

 in the genitalia itself. Where several species have the genitalia 

 identical in form, a figure of those of only one species is given. 



CLASSIFICATION 



The 142 species and varieties of the genus Dasymutilla may be 

 divided into groups, the components of which bear a close relation- 

 ship to one another. Most of these groups are natural ones, but 

 several contain species which are included merely as a matter of 

 convenience, while the last three are purely artificial, including males, 

 the relationships of which are not understood at the present time. 

 The group asopus is a natural one, corresponding to Fox's (1899) 

 groups, waco and asopm combined. The group fulvohirta includes 

 the species fulvohirta and other closely related species. The species 

 cotulla is placed here because the male genitalia and the shape of the 

 last abdominal sternite are like those of the other males in this group, 

 although it differs from those by having a well-developed median 

 pit on the second abdominal sternite. The group thetis includes one 

 species which presents a combination of characters unlike those of 

 any other group. The groups scdbra and foxi are natural groups 

 composed of closely related species. The species included in the 

 group sparsa form a natural group for the most part ; there is, how- 

 ever, some question as to whether niacra should be placed there. The 

 group vesta is composed of one species with its varieties and a second 

 species known only in the male sex which may possibly prove to be 

 only a variety. In the group zelaya, the species zelaya and myrice 

 are very closely related, and the species clytemnestra and coccineo- 

 hirta are very closely related ; the relationship between the two pairs 

 of species is much more distant. The group hioculata is composed 

 of the species hioculata and very closely related species, except that 

 melanippe and its variety and lauta do not show these relationships 

 so clearly. The first eleven species of the group quadriguttata form 

 a natural closely related group, but the last eight species are included 

 on account of the presence of tubercles on the postero-lateral angles 

 of the head, although the tubercles are quite different from those 



