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 b^th Thamnotettix and 
Athysanus; while on the other hand he includes under Delto- 
cephalus species in which the second cross nervura is wanting. 
If the only result of these disarepancies was the misplace- 
ment of a few species with respect to their apparent natural 
affinijties 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 overburdeniog 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 them gene ideally, now appearing 
as a Thamnotettix, now as an Athysanus, or even as Eutettix, and 
seldom failing to get at least one representative ia 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. Seemd, 
species which have two distinct forms, both long winged, one 
form greenish in color and strongly resembling Thamnotettix, 
with only one cross nervure, 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 venation 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 stro*ngly Delto 
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. 
