1897.] THE SPECIES OF THE GENUS MELAXOPLUS. 29 



y\ Prozona of male subquadrate ; supraanal 

 plate with the apical and basal portions in the 

 same plane ; subgenital plate of equal or sub- 

 equal breadth beyond the middle minor, 



j"\ Prozona of male distinctly longitudinal; 

 subgenital plate with the apical portion ele- 

 vated above the median ; subgenital plate dis- 

 tinctly narrowing beyond the middle . confusus 

 i'^. Furcula of male half as long as the supraanal 

 plate ; anal cerci incurved, but otherwise straight. 



arizonce. 

 h^. Furcula of male consisting of brief triangular 

 lobes ; base of lateral margins of subgenital plate 

 not incurved. 



/^. Interspace between mesosternal lobes of male 

 twice as long as broad ; upper fork of cerci 

 scarcely bent upward above the trend of the 

 basal stem. 

 y\ Upper fork of male cerci much shorter 

 than the stem ; subgenital plate shorter thdn 



broad keeleri. 



j'\ Upper fork of male cerci nearly as long as 

 the stem ; subgenital plate of equal length and 



breadth deleior. 



P. Interspace between mesosternal lobes of male 

 scarcely longer than broad ; upper fork of cerci 



bent distinctly upward luridus. 



g'~. Furcula of male absent ; apical margin of subgenital 

 plate not elevated above the lateral margins . collinus. 

 £-. Size medium or large ; cerci of male rarely bifurcate or 

 with an inferior process (and then the insect is of large 

 size, which it never is in the alternate category, and the 

 supraanal plate is distinctly shield-shaped, the apical half 

 tapering with much greater rapidity than the basal; or the 

 furcula is absent ; or the interspace between the mesoster- 

 nal lobes of the male is three times as long as broad, 

 -which it never is in the alternate category) ; supraanal 

 plate of variable shape ; furcula either absent or very min- 

 utely developed ; prosternal spine usually long. 



/\ Interspace between mesosternal lobes of male nearly, 



