INSECT PEST S U H V E I BULLETIN 
LIBRARY 
STATE PLANT BOARD 
Vol, 22 Supplement to No. 3 June 20, 1942 
TSENDS 0E GRASSHOPPER POPULATIONS IN THE AREAS OE 
MAJOR OUTBREAKS 1940 AND 1941 
R, L. Shotwell, entomologist, and 
E. E. Skoog, senior field assistant 
In the general and special grasshopper surveys conducted hy the 
Bureau of Entomology a,nd Plant Quarantine, in cooperation with various 
State entomological agencies, collections have “been ros.de late in the sum- 
mer or fall of adult grasshoppers in the representative crops or habitats 
for each State or section thereof. The specimens in these collections 
were identified and the relative numbers of the species in each environ- 
ment recorded. Erom 1934 to 1939, inclusive, the collecting was general 
throughout the States involved. A series of six supplements to the Insect 
Pest Survey Bulletin contain the data for these years, as follows: 1934, 
vol. 14, No. 9; 1935, vol. 16, No. 5; 1936, vol.’ 17, No. 3; 1937, vol. 18, 
No. 6; 1938, vol. 19, No. 4; and. 1939, vol. 21, No. 5. 
In 1940 and 1941 the collections were made only in three to six 
permanently located representative areas about 20 miles square in each 
of nine Rocky Mountain and Central Great Plains States in which grass- 
hoppers are a major problem, 3eca..use of this change in procedure, the 
data for these 2 years were not treated in the same manner as those for 
the previous 6 years. Together with records of estimated population, they 
are being utilized in a study of trends in the abundance of the different 
species found in the representative areas. 
Usually an outbreak in any given area at any one time consists 
mostly of one, or perhaps two , species, and altogether less than a dozen 
species have been of anj/ - importance in outbreaks. It is therefore be- 
lieved. that the trends of only these few species need be considered in 
evaluating the grasshopper situation. The average numbers of grasshoppers 
and. grasshopper egg pod.s per unit area, as found in the general survey 
data, include all the species, rega.rd.less of their economic importance, 
and. conclusions from such data should be qualified to fit the trends of the 
dominant species. By ad.opting this procedure .any over- or under- evaluation 
of conditions based solely on an annual fall egg survey in known infested 
areas can be qualified or corrected.. 
The following 10 species were included in the tables because of 
their common occurrence and economic importance: 
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