FORAGE LOSSES CAUSED BY RANGELAND GRASSHOPPERS 15 
more severe during periods of high temperatures 
because of the greater amounts of food consumed. 
Parker (1952) also reported that on the basis of out- 
door cage experiments an adult grasshopper of the 
larger rangeland species consumes 30 mg of vegeta- 
tion (dry weight) per day, and because one M. san- 
guinipes consumes 24 mg/day at 27° C as reported 
above, then 74 larger grasshoppers per square 
meter would consume forage equivalent to that of a 
cow. 
Smith (1959) also reported on food consumption, 
utilization, and weight gain of adult Melanoplus 
sanguinipes for 5-day periods on three food plants 
as follows: 
Totals for 8, 5-day periods 
Food plant (40 days) 
Food consumed: Mg dry weight 
Wheat 714.9 
Western wheatgrass 810.1 
Oats 373.0 
Totals for 8, 5-day periods 
Food plant — Continued (40 days) 
Mg dry weight 
Food utilized: 
Wheat 231.7 
Western wheatgrass 259.7 
Oats 119.0 
Gain in weight: 
Wheat 70.2 
Western wheatgrass 68.9 
Oats 43.4 
The utilization of oats differed significantly from 
the other two food plants in all three tests. 
Appendix table 2 contains a summary of forage 
losses from U.S. studies based on field populations 
and the amount destroyed by species during 
nymphal and the adult stages combined. Appendix 
table 3 contains forage losses determined sepa- 
rately for nymphs and adults of individual species 
and/or in the laboratory and field. 
SUMMARY AND RECOMMENDATIONS 
Grasshoppers have been and still are the major 
invertebrate pest on millions of hectares of range- 
land in the Western United States, and much time 
and effort have been given to the research of this 
group. However, little real progress has been made 
to determine the actual amount of forage lost under 
the different grazing situations, and the informa- 
tion available is seldom utilized in control decisions. 
In the United States, grasshoppers are controlled 
by individual land managers, private organizations, 
and by State and Federal Government agencies. 
Expensive and intensive grasshopper control meas- 
ures are based largely upon the number of indi- 
viduals per unit area. Species composition, range- 
land vegetation, watershed management, and 
grazing systems are usually ignored when control 
recommendations are made. 
The role of grasshoppers as grazing animals in 
competition for forage with livestock and wildlife 
needs additional study and one of the basic criterion 
for evaluating this role is the determination of for- 
age losses resulting from a particular grasshopper 
population. However, unstable weather patterns, 
fluctuating grasshopper numbers, and a changing 
vegetational complex make predictions regarding 
forage losses with our present knowledge very 
unreliable or impossible. Therefore, an approach is 
suggested as reported on by White and Watson 
(1972), and White (1974a, 1974b, and 1974c), in New 
Zealand, mainly using field data. 
Grasshopper populations in the major rangeland 
types (northern shortgrass rangeland, southern 
plains area, intermountain region, and coastal area) 
need to be studied in detail in association with the 
vegetation and weather patterns of the area. The 
following information is needed on grasshopper 
populations from the time of hatching until grass- 
hopper abundance decreases to near zero: (1) Den- 
sity, (2) length of each instar, (3) number of feeds 
per day or number of minutes spent in feeding each 
day, (4) amount of forage (mg) consumed or de- 
stroyed per feed or during a certain period of activ- 
ity (time temperature is >21.1° C), and (5) grasshop- 
per mortality resulting from parasites and adverse 
weather conditions. (Predation by birds, mammals, 
and insects is less variable since most of these 
predators are territorial by nature, and, thus, their 
numbers are fairly constant from year to year un- 
less major vegetational changes take place.) 
The above information should be recorded for 
each instar of the more abundant grasshopper spe- 
cies present. In addition, weather data such as 
ground surface temperature, soil temperature and 
moisture, and precipitation need to be correlated 
with grasshopper and plant development, espe- 
cially to predict forage production on the various 
