298 - 
A-Quarent Decrease of Melanoplus meslcanus in Relative Abimdance 
Melanot>lus mexicanus egg pods were fo\and during the egg survey 
in eastern North Dakota and north-central Montana in as great numbers as 
ever in the history of surveys, hut collections of grasshoppers made in 
these States and others of the main M« mexicanus area showed a decided 
decrease in the relative ahimdance of M. mexicanus from 1938 to 1939, 
A Verifi cation of iihis is found in a comparison of the percentages of 
M. mexicanus in tha "collections made on range land and in all habitats 
for these years. These data are given in tables 1 and 1 A, On the 
range land there is a decrease of from 9 to 36 in the percentage, with 
an average of 14 percent for the entire area, For all habitats bhis, de- 
crease is from 7 to 17 percent, with an average of 10 percent. All this 
indicates a downward trend in the numbers of mexicanus . although it 
remains the most important species and was very abundant over large 
areas. 
Table 1, — Decrease of relative abundance of Melanonlus mfixicanus > 
on range land 
State 
M. mexicanus taken 
1938 
1939 
Difference 
Percent 
Percent 
Percent 
Montana - -- -- -- -- - 
54 
18 
-36 
North Dakota (eastern)- 
32 
18 
-14 
North Dakota (western)- 
32 
8 
-24 
South Dakota ----- 
15- 
6 
- 9 
Nebraska ----- 
29 
16 
-13 
Wyoming- ------ - 
29 
20 
- 9 
Entire area ------ 
28 
" 14 
-14 
Table 1 A«- — Decrease of relative abundance of Melanoplus mexicanus 
for a total of specimens collected in all habitats 
M. mexic^us taken 
State 
A X A 
1938 
1939 
Difference 
'Percent 
Percent 
Percent 
Montana - -- -- -- -- - 
63 
46 , 
-17 
North Dakota ------- 
49 
37 
-12 
South Dakota ------- 
40 
28 
-12 
Nebraska ------- 
32 
25 
- 7 
Wyoming -------- 
36 
26 
-10 
Entire area 
42 
32 
-10 
