174 
IOWA ACADEMY OP SCIENCES. 
Some of the results which seem to be general in nature may- 
be mentioned here. 
The species of Jassidse have, as a rule, a decided limitation 
as to food plant, usually holding closely to one species of plant, 
almost invariably limited to one plant for breeding, but feeding 
more indiscriminately in maturer stages. 
So far as known, all the species deposit eggs upon the stems 
under the leaf sheaths or in the leaves of the plants used as 
food. 
There is a wide difference in life-histories, some having one 
brood, the majority of the grass-feeding species two, and still 
others three in a season, and the successive stages occurring at 
widely different times. 
Except in the case of adult hibernation the ordinary life of a 
brood of adults does not exceed two months, and for the indi- 
viduals of a brood rarely over one. The males appear a week 
to ten days before the females and disappear as much earlier. 
In general, one brood of adults will have disappeared before 
the larvae of the next have matured, so that individuals col- 
lected at any time may be referred with assurance to a partic- 
ular brood. 
It follows also that eggs for each brood are deposited within 
a limited time and that a period may be defined during which 
all eggs of a given brood for a given species will have been 
deposited, and during which time measures for their destruction 
may be applied. 
Observations were made to ascertain whether simply cutting 
the grass and leaving it in the field would prevent hatching, and 
in no case were eggs observed to hatch from stems cut green. 
Part of the stems from a plant in which eggs were fully devel- 
oped were cut and left to dry. The second day after the eggs 
hatched in the uncut stems but no larvae issued from those that 
were cut and, on examination, the eggs were found to be crushed 
and distorted from the shrinking of the plant tissues and by 
the curling of the edges of the sheaths in drying. Even if 
hatched they would have been unable to escape from the rigid 
incurved edge. 
It has been learned that the larvae present definite characters 
which are of specific, and in some cases generic, value. These, 
along with what prove to be constant characters in large series 
of adults, enable us to combine some forms hitherto considered 
