26 CIRCULAR 2 41, U. S. DEPARTMENT OF AGRICULTURE 



THE DESTRUCTIVE LEAF HOPPER 



The destructive leaf hopper (Euscel'is) Exitianus obscurinervis 

 Stal, was first given definite recognition as a destructive pest in the 

 report of the entomologist of the Department of Agriculture in 

 1879 (4, P- 191-193), and in connection with this report there is 

 given a technical description of the species under the name Oicadula 

 exitiosus Uhler. While it seems impossible that the injuries of the 

 insect should have escaped previous observation, it is probable that 

 they were referred to some other insect or that the injury was not at 

 that time charged to any insect. This report mentions damage dur- 

 ing the previous winter to grain in western South Carolina, parts of 

 North Carolina, and Georgia, and shows that the leaf hopper 

 occurred in immense numbers and did great injury to the crops. 



In observations during the summer of 1930 through the drought- 

 stricken district of Ohio, Indiana, Missouri, and Kansas this species 

 was the one which seems to have survived most successfully, as it was 

 found in practically all locations where there was any vegetation 

 sufficient to furnish a food supply. In many cases it was the only 

 species to be found, and in some cases where the growth of alfalfa 

 or some grasses was sufficient to give it abundant food it was found 

 in considerable numbers. This would seem to bear out the supposi- 

 tion that the species has migrated into this region from the Tropics, 

 and it shows also that it has a considerable range of host plants 

 which permit it to survive where other species are eliminated. 



DESCRIPTION 



The adult insect (fig. 9, a) of this species is about one-sixth inch 

 in length, the males being somewhat smaller than the females. The 

 color ranges from dark, nearly black (especially in individuals from 

 the Southwest) to grayish white, the wings especially being almost 

 transparent, but showing very distinct dark veins. The head is 

 broad, and the body tapers quite distinctly to the tip of the wings, 

 the widest part of the body being about one-fourth the distance from 

 head to the end of body. The eggs which were secured by dissec- 

 tion from an adult female are about 1.5 to 2 mm long and 0.5 mm 

 thick, distinctly enlarged near one end and tapering to a rather dis- 

 tinct, blunt point at the other end. They are placed in the leaves or 

 between the leaf sheath and stem of the plant. 



Comstock states that the young hoppers when hatched are almost 

 or precisely the same in appearance as the old ones, except that they 

 lack the wings. There is, however, a slight difference in the position 

 of the spots on the head and in the proportion of the parts of the 

 body, the head appearing considerably larger in proportion, this pro- 

 portion decreasing as the young insect develops. The head is broad, 

 the eyes prominent, and there are two distinct black spots on the 

 front portion of the head surrounded by a lighter circle, and the body 

 is marked with grayish dots, both on the thorax and abdomen. As 

 the nymph grows the wing pads develop at the sides and in the final 

 stage extend back over the base of the abdomen. These characters 

 may best be seen in Figure 9, which shows also three nymphal stages. 



