302 - 
This gave some advance knowledge of when to. expect hatching. Table 3 shows 
the sxims for the main stations in the M,. mexicanus area,' 
Table 3,-— ‘ Soms of Degrees of Dally Maximm Temperatures Above 
60° in the Spring Before Hrat Hatching of M. mexicanus 1/ 
Station 
Date of 
first -hatch 
Sum of' 
degrees 
Valentine, Hebr, r-- 
- , April 24 
y', ' 172-' y : '■ ■ 
Newcastle, Wyo, _ - - _ 
April 28 / ’ 
... . •■■■■ 150'v ■'■ ■■■ 
Willis ton, N, Dak, 
' May 1 
Bismarck, N, Dak,- 
May, 'i . , 
1D6 
Dickinson, N, Dak, - - - - - 
May 1 
194 
Grand Porks, N, Uak, _ - _ 
May 6 
' 178 
Lead, S, Dak, 
May 13 
160 
2J M. bivittatus was reported hatching along with M. mexicanus . 
The accvnnulative temperatures for G-rand i’ofks, amounted to 
114 on and including May 2 and as yet no hatching- had been reported for 
tha.t area. It was predicted that hatching would take place in this area 
within the next 3 or 4 days, provided inaxilaium air' temperatures rose above 
70°. Hatching did take place at this time as shown in ta1)le 3, During 
the 3 days after May 2, 64*^ more above 60°. m.aatiniuia were added to the total 
of 114°, making a total of 178° before hatching was. observed. 
In the Black Hills area, hatcl^ng. was .from 7 to 25 days later than 
in the open— plains areas. This was due to lower temperatures and more 
moisture, Hirst hatching was estimated to be a^bout May 13, because on 
May 19 a collection of nymphs showed 60 percent first instars and 40 per- 
cent second instars. By May 13 daily maximum 'temperatures above 60° had 
totaled 160°, It is believed that this ^ves,.a rough method for predict- 
ing the date when hatching will begin,, ; ’ 
Hor the whole area, fields of ^ali-gfain stubble covered with 
Hus si an— thistle were;; the most common, source, of infestations for M. mexicanus 
Other sources were i4*ile land, pure stand? of alfalfa, native grass-hay 
meadows, depleted range land, buckbrush draws,^ river bottom, and bench. 
Remarkably few M. mexicanus were present on! good gramar-grass range land. 
This was especially noticeable, where the grama_ grass grew up to the edge 
