8 MISCELLANEOUS PUBLICATION 1348, U.S. DEPARTMENT OF AGRICULTURE 
under field conditions, the greater portion of the 
energy that results in raising the body temperature 
of grasshoppers comes from the absorption of direct 
solar radiation. Some species differ in their ability 
to absorb radiant energy, and, thus, grasshopper 
feeding may be affected by such differences. These 
authors also report that grasshoppers climb on 
vegetation to orientate themselves to the sun’s rays 
during cool weather, such as in the fall, and may 
remain in that position throughout the day. This 
may result in reduced feeding. 
In New Zealand, White (1974a) measured the 
incidence of adult grasshopper activity relative to 
the level of insolation and determined that a decline 
of activity begins when insolation approaches 2.0 
cal cm * min '. He also monitored the temperature, 
or the temperature at which grasshoppers become 
active in the base of plants, and found that the 
threshold temperature approximates 3° to 4° C. 
However, weather indirectly affects grasshoppers 
through its direct effect on vegetation. 
Nerney (1960, 1961) and Nerney and Hamilton 
(1969) reported that on poor or overgrazed range- 
land, grasshopper populations are greater after 
years with normal or above-normal precipitation 
than after those with unusually light precipitation. 
Apparently, average or above-average precipita- 
tion allows more plant species to become available 
for grasshopper feeding. In Arizona, spring-hatch- 
ing species are of greater economic importance, and 
outbreaks occur more frequently than with the 
summer-hatching species. Thus, early rainfall is 
important to the development of grasshopper popu- 
lations in Arizona. This situation is different from 
that in the Great Plains where overgrazing, ero- 
sion, and drought are usually associated with grass- 
hopper buildups. In this area, during times of cool 
weather and abundant rainfall, grass is likely to be 
plentiful, and the amount consumed by grasshop- 
pers may not be economically significant. In hot dry 
weather, however, grass is likely to be scarce, and 
the amount consumed by grasshoppers may be very 
important. Certainly, the weather pattern in any 
one area may favor certain plants and tend to de- 
crease or eliminate others. Perhaps as a result of 
these vegetational changes, food and shelter condi- 
tions might be produced that would be either more 
or less favorable to different grasshopper species. 
Some authors have also reported that early warm 
weather followed by cold weather can cause a high 
grasshopper mortality (Shotwell 1929; Parker 
1928). 
Physiological Influence 
Only general statements can be made regarding 
the amount of food consumed by grasshoppers dur- 
ing their development. Langford (1930) pointed out 
the wide variation in the amount of food eaten by 
individuals of the same brood hatched from the 
same egg pod and reared under the same condi- 
tions. 
Anderson (1970) stated that whether a popula- 
tion is vigorous and increasing in numbers or 
lethargic and decreasing may have an effect upon 
the amount of vegetation destroyed. He felt that 
when a population grows individuals spend less 
time fighting among themselves and more time 
feeding. Conversely, a population that has reached 
peak numbers or is decreasing seems to be more 
excitable and spends less time feeding. Generally, 
food consumption in Orthoptera increases in direct 
proportion to size during nymphal stages (Gang- 
were 1959). Langford (1930) remarked that with 
each molt a grasshopper almost doubles the amount 
of food eaten daily. His laboratory tests with Mela- 
noplus differentialis (Thomas), M. bivitattus (Say) 
and M. femurrubum showed that adult females eat 
almost 100 times more food per day than first instar 
nymphs. 
Smith (1959) studied Melanoplus sanguinipes in 
the laboratory and found no difference in the 
amount of food consumed and utilized between the 
sexes. Langford (1930), on comparing 113 males 
with 94 females, found that the females ate from 1.8 
to 3.6 or an average of 2.5 times more food than 
males in a 12-hour day. The female ate from 8.0 to 
260.5 percent more food per day than the males. 
Matsumoto (1971) conducted laboratory feeding 
tests in Japan and also found that females ate more 
than males. 
Gangwere (1959) explained that while females of 
a species eat more than males, they eat less per unit 
of weight, as would be expected from their lesser 
activity and lower metabolic rate. He says the con- 
sumption ratio between male and female is rela- 
tively constant even under fluctuating environ- 
mental conditions, for changes in temperature and 
humidity alter gross consumption without affecting 
the ratio. 
