FORAGE LOSSES CAUSED BY RANGELAND GRASSHOPPERS 5 
stages showed a preference for grasses and sedges. 
Ueckert (1968) confirmed this species preference 
for grasses and sedges but concluded that prefer- 
ence for sedges decreased as the season pro- 
gressed, whereas the preference for wheatgrasses 
and Idaho fescue, Festuca idahoensis Elmer, in- 
creased. Misra (1962), working with Camnula pellu- 
cida in the laboratory, concluded that the grasses 
best for survival and development changed weekly 
so that grasses which were best in the early stages 
of development may retard development in the 
later stages. He concluded a mixed diet would be 
most beneficial. 
Gyllenberg (1969) studied food preferences for 
Chorthippus parallelus (Zett.) in Finland and con- 
cluded that the adults consumed mainly the same 
plant species as the nymphs, except for herbaceous 
plants that were only eaten by the nymphs. In the 
laboratory, the adults consumed grasses exclu- 
sively and the choice was widest during the third 
instar. Studies by Ueckert (1968) and Ueckert and 
Hansen (1971) showed that food preferences of a 
grasshopper species usually change seasonally, 
especially during the adult instar. This seasonal 
change in diet may be related to forage maturity 
and availability and to changing nutritional needs of 
the grasshopper. Allred (1941) reported that grass- 
hoppers, mainly Aulocara elliotti and Ageneotettix 
deorum, which prefer grasses, killed 50 percent of a 
big sagebrush stand along the Little Powder River 
in Wyoming and Montana. On another occasion, M. 
sanguinipes fed readily on sagebrush over large 
areas in eastern Montana in 1939 even when mois- 
ture and grasses were available. 
The demand on the food resource is spread out 
over an entire growing season, and a plant may be 
preferred by some grasshopper species during veg- 
etative and succulent stages and by others during 
reproductive or wilted stages. Ueckert and Hansen 
(1971) found that plants are commonly more highly 
preferred when they are dried and wilted than 
when succulent. 
Bernays et al. (1974) showed that the amounts 
eaten by Locusta migratoria migratorioides (R. & 
F.) on seedling grasses were less than on mature 
grasses. They found a higher grasshopper mortal- 
ity with those grasshoppers that fed on the seed- 
lings as compared with the mature grasses at all 
stages of nymphal development. Additional tests 
showed that an inhibitory substance in the seedling 
leaves was probably acting as a feeding suppres- 
sant. 
Grasshopper Density 
Changes in grasshopper density throughout the 
summer must be considered when damage is re- 
lated to the number of grasshoppers per square 
meter (Anderson 1972). Nakamura et al. (1971) 
discussed the population dynamics of a Japanese 
grasshopper population and concluded that Para- 
pleurus alliaceus Germar decreased from 268 per 
square meter at the early nymphal stages in June 
to 68 adults per square meter in mid-August. Early 
instar mortality seems to be common with many 
species of grasshoppers, and parasites and preda- 
tors also feed on later instars and adults. Hastings 
(1971) studied different populations of Aulocara el- 
liotti to detect differences that could be correlated 
with grasshopper density; however, no direct rela- 
tionship could be shown. 
Kajak et al. (1965), in Poland, studied the effects 
of spiders on grasshopper populations by using 
cages covering 0.64 m’. He concluded that, on the 
average, the presence of spiders reduced by about 
two times the losses in plant yield caused by the 
grasshoppers. Therefore, spiders may exert a sig- 
nificant influence on grasshopper populations and, 
thus, on the plant yield if grasshoppers and spiders 
are in the environment at the same time. However, 
as pointed out by Parker (1952), some species are 
early, others are intermediate, and some are late in 
hatching, reaching the adult stage, and ovipositing. 
Differences of 4 or 5 weeks have been found be- 
tween early and late-developing species in Montana 
and Wyoming. Thus, grasshopper density is contin- 
ually changing during the grasshopper season. 
Habitat Preference 
Vegetation definitely plays a role in determining 
grasshopper distribution and abundance beyond 
that of providing a source of food. A number of 
workers have described the preferred habitats of 
rangeland species. Clark (1947) found the optimal 
ovipositional habitat for the Australian plague lo- 
cust to be areas lacking vegetation exceeding 15 
centimeters in height with approximately 50 per- 
cent bare ground and 50 percent low cover. The 
optimal food shelter habitat of old nymphs and 
