May 1965 ARS 33-102 
UNITED STATES DEPARTMENT OF AGRICULTURE 
Agricultural Research Service 
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WATIONAL Anim, oo 
FORECASTING THE HATCHING PERIOD OF GRASSHOPPERS SESE TBD 
FROM WEATHER DATA Belt sled 
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By R. L. Shotwell” Ee Bani Ab 
Entomology Research Division 
The earliness or lateness of the hatching period of grasshoppers 
affects the type and amount of damage to the crop and the timing of control 
measures. The method most commonly used for determining the status of the 
hatch has been to have an observer in the field making a spot examination 
during the months when hatching is likely to occur and then a judgment of 
what he finds. The accuracy of the data is one of individual judgment. 
Laboratory experiments substantiated by field observations have shown 
the significant effect that temperature nas on the rate of embryonic develop- 
ment and the subsequent hatching period.2 In the field daily maximum air 
temperatures have been the best criteria of warm weather conditions in their 
relation to the time of hatching, and their use for unit intervals of 5 days 
each is better than using monthly averages in this type of analysis. These 
daily temperature units have therefore been basic to the development of a 
method for currently predicting the hatching period. 
This report pertains to the hatching period of the end or surviving 
infestation made up of those grasshoppers that have survived all the 
natural factors that tend to destroy early instar nymphs. It is not the 
true hatching period for all the infestation, but it is the one that 
concerns the farmer and the control supervisor. 
All the data used in the subsequent analyses were obtained from records 
of grasshopper collections made in the field by trained observers from 1939 
through 1948 in Kansas, Minnesota, Montana, Nebraska, North Dakota, South 
Dakota, and Wyoming. The collections were made at locations near a Weather 
Bureau station recording daily maximum and minimum air temperatures and 
rainfall. The grasshoppers from these collections, made at intervals 
1/ Retired June 30, 1958. 
2/ Shotwell, R. L. Life histories and habits of some grasshoppers of 
economic importance on the Great Plains. U.S. Dept. Agr. Tech. Bul. 774, 
ATmeppie suoenlee 
