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



other species in numbers. In a statement of relative abundance by 

 Wildermuth (19, p. IS) it was shown that this species may comprise 

 about nine-tenths of the numbers captured. Although bluegrass and 

 timothy are the more common food plants, the species has a wide 

 range and has been observed on wheat, oats, millet, corn, rye, clover, 

 alfalfa, and a considerable number of wild grasses of the Plains 

 region. This general occurrence on different food plants makes it 

 possible for the species to survive in almost any locality, and it is 

 thus given abundant opportunities to migrate to any favorable crop 

 which may grow within a reasonable distance. 



LITE HISTORY 



Although the nymph was mentioned by Say in his original de- 

 scription, no study of the life history seems to have been made until 

 1892. General descriptions of the different stages have been made 

 by the writer (17, IS). The eggs are deposited in the leaf or stem, 

 especially beneath the epidermis of bluegrass, and cause very minute, 

 blisterlike swellings. These for the winter generation remain until 

 spring and hatch, for the latitude of Iowa, in the latter part of 

 April and early May, there being some variation according to the 

 season. This generation matures by the latter part of August, and 

 adults are usually encountered from this time on until winter, 

 although scattering nymphs are likely to occur during the fall 

 months. No proof, however, is available of a definite third brood 

 for the season, and eggs deposited by adults in the fall survive the 

 winter, to renew the cycle the following year. 



During the growth of the nymphs five distinct stages have been 

 observed, the first of Avhich, the newly hatched nymph, is rather 

 short, with a very prominent head and a small abdomen, and with- 

 out clear markings. The second stage differs in having a more 

 elongate form of body and a definite black border along the sides 

 of the thorax and abdomen. The third stage differs from the second 

 only in the appearance of the wing pads, and from this stage on 

 through the fourth and fifth stages the change consists merely in 

 a greater intensity in coloring and relative increase in the size of 

 the wing pads. At the end of the tibia of the hind legs there is a 

 peculiar microscopic spatulate structure that occurs in varying num- 

 bers from the newly hatched nymph to the adult form. In the 

 specimens studied and figured there were for the first instar 1, for 

 the second instar 2, for the third instar 3, for the fourth instar 5, 

 and for the adult insect 5. The adults are gray, with dark-brown 

 or blackish markings. A very constant feature is the presence of 

 3 pairs of black spots, 1 pair on the vertex, 1 pair on the pronotum, 

 and 1 pair on the scutellum. The length is about one-fourth of 

 an inch. 



The molts occurred at intervals of 7 or 8 days in specimens ob- 

 served in rearing cagos, and in some instances the development 

 from the newly hatched nymph to the adult occurred in 32 days. The 

 time of incubation for some eggs has been determined as not longer 

 than 17 or less than 10 days. This, however, was for eggs kept 

 in jars, and it is possible that under outdoor conditions the rate 

 of development may be more rapid. 



