- 30X - 
In the southern areai J. A, Gillett found that stuhhle fields deeply 
plowed were comparatively free from grasshoppers. Spring grain which had 
"been disked or stuhhled-in hastened hatching hy removing the weed cover and 
fields stuhhled-in had the most grasshoppers. At the time of hatching the 
wheat planta were frc«n 2 to 4 inches high and very susceptible to total 
damage, . , . 
In table 2 there are also shown population trends for the main crops 
and habitats in the M. bivitt'atus and M, differentialis areas in South 
Dakota, ilebraska, and Iowa, Comparing trends in this area with those in 
the main M, mexicanus areas, one notes that the peak of population was 
reached more slowly, probably because of a slower rate in hatching, ThS 
greatest difference was in the margins, in which there was a big diffe3>- 
ence in the quantity of plant cover \d.th taller and heavier sod and weed 
conditions in the M, bivittatus-differentialis areas. 
Further study of table 2 shows that small graih stubbled into com 
or sorghum- had 2-l/s times as many grasshoppers as did the grain sown in 
deep-plowed com or sorghum stubble. It also shows that“ ho'^ grasshoppers 
appeared in the grain on plowed land until 3 weeks after they had hatched 
in the stubbled-in grain. The infestations in the grain oh plowed land 
were caused by grasshoppers moving in from outside soiu*ces. Grasshoppers 
did not appear in the corn until the week of June l7, which was 5 or 6 
weeks after hatching had begun. From the peak, of the nymphal infestations 
to the adult survey on August 19, poinxlations fell off 90 'percent. 
It was observed that within a day after alfalfa was mowed, and raked 
most of the nymphs beyond the third instar in development had moved to the 
edge of the field or into adjacent crops. When new plant growth started 
the grasshoppers often moved back,, Date in June, when the grain. or alfalfa 
was harvested, the com was invaded, local movements consisting of shift- 
ing flights of M, bivittatus and M, differpatialis began on a large scale 
about July 6 and continued into August, , . ... 
Melanoulus. mexicanua Arfla 
This area embraced the eastern third of Montana, the western half 
of North Dakota, eastern Wyoming, the Black Hills section of South Dakota, 
and western, or Panhandle section of Nebraska, The survey supervisors 
working in this area were J, A, Gillett and F, S, Skoog, The following 
account is based on their observations, • 
Hatching of M. mexicanus began on, April 25 and extended to June 1, 
with a general hatch the first week; of May, In this area M, bivittatus 
was reported as ha.tching along with M, mexicanus . 
For M, mexicanus and M, bivittatus it was known that in the spring 
additive amounts of daily maximTam air temperat-ures above 60° F," would have 
to equal from 150° to 200° before hatching began. Therefore, progressive 
daily totals of the numbers of degrees the maxima went above 60° were kept 
for important stations scattered throughout the entire infested area. 
