LEAFHOPPERS OF THE SUGAR BEET. 45 



Hoon as the little nymphs begin to feed, and this is soon followed by 

 the distortion of the leaf in a certain definite Avay 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 piguient or 

 the gall-like distortion. The fact that a certain characteristic color 

 and appearance are alwaj's 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. 



AMiether 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 leafhoppers present, the injury appeared onlj^ after the 

 appearance of the leafhoppers, and the " curly-leaf " condition is 

 known to occur only on beets growing within the range of this insect. 



Attention was not called to the damage earl}'' enough in 1905 to 

 ascertain whether or not the " curly-leaf " appeared before the first 

 appearance of the nymphs. At Lehi, Utah, the " curh'-leaf " ap- 

 peared very soon after the first nymphs. In the Cache Valley, Utah, 

 the nymj)hs were common by the time the first curling was noticed. 

 In 190G 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 tlie 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 tiie curled beets than on others. At first this was 

 thought to show a gregarious habit in the adidt, 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 Eiitetti.v stroh'i 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 cases but a single nymi)h will be found 

 on a plant, and sometimes the adult and the nymphal skin of each 

 stage may be found under a single leaf. It is very likely that the 

 same habit persists in Eutettix tenella and that this fact, in part at 



G6 — IV 



