THE BLACK-FACED LEAFHOPPER. 77 
could observe, but twice afterwards. December 22 one of the first individuals to 
appear molted for the last time, and on the following day adults were out in numbers. 
It will be observed that 41 days were required for the development of the insect from 
egg to adult. It is not unlikely that the species hibernates in the egg state in the leaves 
of grass, though it would seem probable that it may also live over as adults. My wheat 
plants were kept growing in glass tubes, probably an inch and a half in diameter, and 
in a temperature of probably not far from 70° F. ("Webster, Ohio Agr. Exp. Station 
Bui. 68, p. 43, 1896.) 
TREATMENT. 
There is not much to be added to the discussion of general treat- 
ment, as this species is one of the most widely distributed and is 
open to every remedy which has been advised for the leafhoppers in 
general. The fact that it is primarily a grass insect and that it 
attacks wheat, oats, and other grains incidentally, makes it possible 
to restrict its injuries to other than grass crops by attention to the 
fields adjacent to such cultivated crops. The burning of grass along 
the sides of the field, in fence corners, or along roadsides would in a 
large degree protect wheat fields from the fall migrations. The species 
is readily caught in the hopperdozer, and in pastures or permanent 
meadows where burning is not considered desirable this or the appli- 
cation of an insecticide by spraying is probably the most available 
remedy. 
The Black-faced Leafhopper. 
(Deltocephalus nigrifrons Forbes.) 
The black-faced leafhopper (Deltocephalus nigrifrons Forbes) is an 
abundant and very widely distributed species, occurring in a very 
perplexing number of variations, so that it has received several dif- 
ferent technical names. It was first described by Prof. S. A. Forbes 
from specimens found depredating in wheat and oats, but no details 
of life history were given and, apparently, no detailed study of its 
habits or distribution. Since then little has been done in the way 
of working out its habits and, aside from a publication of a record 
of its occurrence on different food plants and a description of the 
lymphal stage in 1907 by Osborn and Ball, very little has been 
published. 
It is one of those perplexing aggregations which are the despair of 
systematic workers and which are excellent examples for the evolu- 
tionist, since the different variations run off into such extreme forms 
as to indicate the possibility of incipient species. We need not con- 
sider in detail the systematic problems, however, as apparently for 
this species these do not have any very great economic significance. 
If it were a question of the economic importance of separate varieties 
this question might be much more essential. So far as determined, 
however, all of the forms will migrate readily from one plant to 
another and consequently no restriction corresponding with these 
variations is to be considered. 
