IOWA ACADEMY OP SCIENCES. 195 



may be reduced with a reasonable degree of certainty to three: 

 A. scoparins, B. hirsuta and curtipendula, and from its scarcity in 

 a field of nearly pure scoparius its probable host is a Bouteloa. 

 This agrees well with its known habitat, which corresponds 

 with that of these grasses. 



REVIEW OF THE GENUS DELTOCEPHALUS. 



This genus is distinctively a group of grass-feeding species, 

 probably the most important in this relation on account of its 

 wide distribution and large number of species occurring 

 annually in immense numbers. 



The genus was originally founded by Burmeister, who char- 

 acterized it as follows: Vertex acutely triangular, distinctly 

 margined; width between eyes scarcely equaling length; front 

 broad, convex; vertex flat. Fieber in his synopsis of the Del- 

 tocephali adds the presence of two cross nervures between the 

 forks of the first sector and the second, as a sub -family char- 

 acter. Later writers have omitted the head characters and 

 depended upon the cross nervure alone for group separation. 

 Mr. VanDjzee, to whose careful and accurate work we owe the 

 greater part of our present knowledge of the American Jassidse, 

 seems to have accepted and used this character against his own 

 better knowledge and judgment, for, in Entomologica Amer- 

 icana (vol. v., p. 93) he says: "This apparently trivial and not 

 infrequently variable character seems almost inadequate for use 

 in separating these two genera, but, correlated as it is with 

 other structural peculiarities, of which it is the most pro- 

 nounced, it appears to answer well the purpose of its employ- 

 ment, and is much used by Pieber and other European entomol- 

 ogists in synoptical arrangements of the genera." A few years 

 later he described Athysanus instabilis, extriisus and sexvittatus, 

 placing them correctly in that genus despite the fact that most 

 of the types exhibited the two nervures, thus showing that he 

 appreciated the true generic character. The next year, how- 

 ever, he again yielded to the demands of this variable char- 

 acter and redescribed D. nigrifrons as Thamnotettix perpunctata, 

 although evidently appreciating their specific affinity, as seen 

 by the following extract: "Tnis insect, though quite distinct 

 generically from D. nigrifrons, is difficult to distinguish in spe- 

 cific characters; the markings are almost identical, and the 

 form of the facial and genitil pieces differ but little." Dr. 

 Melichar, in his recent work on The Homoptera of Middle 



