202 



of evolution is not confined to the Alolilni, bnt is found in 

 each of the main divisions of Delphacidae; in the Delphacini 

 it appears in several groups, evidently without any phylo- 

 genetic significance. In other families of Fulgoroidea it is 

 also observed; in the Derhidae (i. e. Tiraha and Kaha) this 

 narrowing of the frons is carried to such a degree as to sug- 

 gest hvpertcly (if it were of any use at all). In Zoraida we 

 have an extreme case of narrowing of the frons at the last 

 ecdysis, not by an actual lessening of the surface, but by a 

 longitudinal invagination of the frons, the lateral edges form- 

 ing the entire frons in the adult. It is highly probable that 

 in Viviha and Kaha a reverse process takes place, the face 

 evaginates and collapses together. At present the nymphs of 

 these two genera are unknown. 



In the elongation of the head of DirtyophorodeJphax we 

 have a process which has taken place in other groups of Del- 

 phacidae (i. e. Tropidocephala and Emholophora) and in other 

 families of Fulgoroidea. 



The specific characters can be divided into two groups, 

 chrootic''' and phallic. The former consist of slight variations 

 in length of antennae, length of furcation of frontal carina, 

 length of tegmina, slight differences of texture of tegmina, and 

 in differences in coloration. Among these characters I can 

 detect no direct line of evolution which would fit more than 

 one character, so that we must admit a great deal of parallel 

 development. The phallic characters are more definite. Lei- 

 aloliae is a group in which the aedeagus appears to proceed 

 from a form with a small crook at apex and a small spine on 

 the right side near apex, to a foi-m in which these are very 

 long and narrow, and to a form in which a third spine ap- 

 pears at apex. In one group of Nesodryas the third spines 

 become larger, while in the other gi-oup the crook disappears ; 

 N. freycinetiae appears to be an extreme development of the 

 latter. The genital styles appear to proceed from a sickle- 

 shape to a much straighter form. 



In the Alohae the diversity is much greater and some dis- 

 tinct groups are formed, some of which are very isolated. In 

 Aloha ipomoeae we have a fairly primitive type, and also in 

 Nesosydne hoae, the latter having several allied forms ; in 



♦Sharp and Muir (Trans. Ent. Soc. Lond. 1912, III, p. 602) used 

 this term to indicate the body wall apart from the phallic structure. 



