196 IOWA ACADEMY OF SCIENCES. 



Europe, uses this single character in his synoptical arrange- 

 ments as a primary basis of division for separating groups of 

 genera, but evidently does not accept it in his distribution of 

 species, as he places species that possess the two cross nerv- 

 ures in connection with a similar forking of the first sector to 

 that laid down for the deltocephali in both Thamnotettix and 

 Athysanus; while on the other hand he includes under Delto- 

 cephalus species in which the second cross nervure is wanting. 



If the only result of these discrepancies was the misplace- 

 ment of a few species with respect to their apparent natural 

 affinities it would not be worth while, in consideration of the 

 chaotic condition of other jassid genera, to attempt to restrict 

 one genus at the expense of still more overburdeitiug others. 

 But upon an investigation of the actual conditions existing it 

 has been found that species variable in this respect exist in 

 large numbers, and that they have been and are being described 

 over and over again under different appellations, according as 

 their variable venation places tham gaaerically, now appearing 

 as a Thamnotettix, now as an Athysanus, or even as Eutettix, and 

 seldom failing to get at least one representative in Deltocephalus. 



The variable species may be roughly divided into three 

 classes: First, those species which vary between the opposite 

 sides of the same individual, or between two individuals other- 

 wise exactly alike. Athysanus extrusus and sexvittatus and D. 

 concentricus are good representatives of this class. Second, 

 species which have two distinct forms, both long winged, one 

 form greenish in color and strongly resembling Thamnotettix, 

 with only one cross nervare, the other form darker, with sub- 

 hyaline elytra, possessing two cross nervures, and the other 

 accompanying changes, notably the constriction of the central 

 anteapical cell. D. nigrifrons, with its list of synonyms, well 

 illustrates this group. Third, a group in which there are two 

 forms with radically different elytra; one in which the wings 

 are abortive and the elytra only cover the second segment of 

 the abdomen; the vanatioa simple, often rudimentary. In this 

 form the female abdomen is usually very long, ending in an 

 attenuate ovipositor; the male abdomen short, with much 

 enlarged genitalia. The other form, with well developed wings 

 and elytra; the venation variable, but usually strongly Dalto- 

 cephaloid; both male and female abdomens normal. The forms 

 described as D. argenteolus and minutus, and as Athysanus gam- 

 maroides all possess these two forms. 



