LEAFHOPPERS OF THE SUGAR BEET. 45 
soon as the little nymphs begin to feed, and this is soon followed by 
the distortion of the leaf in a certain definite way in each case. That 
this is not caused by the mechanical injury of the puncture or due 
alone to the loss of sap seems to be abundantly proved by the fact 
that the Chenopodium is often attacked by other sucking insects in 
much larger numbers without producing either the red pigment or 
the gall-like distortion. The fact that a certain characteristic color 
and appearance are always produced by a given species, no matter 
whether on a Chenopodium or on a sugar beet, and that the color and 
form vary for the different species of the same genus even when 
working on the same plant, would indicate that there is some definite 
agency back of it all. It has also been noticed that in all this group 
the greatest amount of damage is done in hot, dry situations. 
Whether or not the " curly-leaf " condition is entirely the result of 
the change in the beet caused by the attack of the beet leaf hopper is 
still an open question, but that there is some relationship between the 
leafhopper attack and the " curly-leaf " does not seem to admit of a 
doubt in the light of the facts brought out in the investigations. The 
amount of damage in a given valley was directly proportional to the 
number of leaf hoppers present, the injury appeared only after the 
appearance of the leafhoppers, and the " curly-leaf " condition is 
known to occur only on beets growing wdthin the range of this insect. 
Attention was not called to the damage early enough in 1905 to 
ascertain whether or not the " curly-leaf " appeared before the first 
appearance of the nymphs. At Lehi, Utah, the " curly-leaf " ap- 
peared very soon after the first nymphs. In the Cache Valley, Utah, 
the nymphs were common by the time the first curling was noticed. 
In 1906 very careful watch was kept in all parts of the State for the 
very first sign of leaf -curl, and in no case did it appear (except on the 
mother beets) until after the nymphs began to hatch out. In fact, in 
almost every case examined the cast skins of nymphs could be found 
on the back of curled leaves, while on healthy beets these were very 
seldom found. In all observations of both years more leafhoppers 
were found on the curled beets than on others. At first this was 
thought to show a gregarious habit in the adult, but it may be due to 
the fact that a given female lays most of her eggs on a single plant 
and the nymphs tend to remain there. In Eutettix strobi and the 
other leaf-curling forms, where the nymphs are brightly colored and 
depend on their discolored spots for protection, it is not unusual for 
a given nymph to pass its whole life on a single leaf, or on two or 
three adjoining ones; in most eases but a single nymph will be found 
on a plant, and sometimes the adult and the nymphal skin of each 
stage may be found under a single leaf. Tt is very likely that the 
same habit persists in Eutettix tenella and that this fact, in part at 
