1971] Willey & Willey — Populations of Grasshoppers 333 
numerous beaver. The forests form a barrier between each drainage. 
There are many upland meadows surrounded by forest forming a 
natural system of isolated habitats for grassland-dependent animal 
species such as Arphia conspersa. Below 9300 ft elevation, we have 
determined that sage brush (Artemesia tridentata) becomes a domi- 
nant shrub and mixed with oak brush (Quercus gamhellii) , service- 
berry ( Amelanchier pumila) , mountain mahogany ( Cercocarpus mon- 
tanus) and chokecherry (Prunus melanocarpa) form a dense chapar- 
ral on the edges and slopes around the mesa. 
The climate is subalpine with heavy and continuous snow cover 
5 to 6 ft deep, usually from November through April (William 
Knott, weather station records and personal communication). An- 
nual precipitation is quite variable; X from 1956 to I97 1 is 29.7 
inches (S.D. = 6.6), two-thirds falling as snow. The snow pack 
is variable in length; X from 1956 to 1971 is 203 days (S.D. ^ 
17.5). Insolation is high during May, June, and July with our 
Belfort pyrheliograph reading as high as 1.6 cal/cm 2 /min. Air tem- 
peratures during the summer months range from freezing at night 
to 25 °C during the day. The area is subject to unseasonal snow- 
storms, periods of heavy rainfall and alternating saturated and 
dried-out soil. For example, on 26 June 1969, there was a wet snow- 
fall of 6 to 12 inches. On 12 October 1969, a wet snowfall of 24 
inches followed a week of heavy rains wdiich saturated the soil. This 
snowfall formed the basis for a continuous dense snowpack above the 
9000 ft level until 15 May 1970. This early and continuous snow- 
pack (216 days), just within one standard deviation, and long water 
saturation of the soil was unique in the memory of William Knott, 
whose family has kept precipitation and temperature records on the 
mesa since 1905. The snow pack of 1 970-71 was equally long, but 
started as a dry, cold snowfall. Again on 12 June 1970, there was 
a snowfall of 14 inches, which melted within a couple days. How- 
ever, the snowpack records of the climatological station show that 
these last two winters were not the longest packs on record ; that 
of 1956-57 lasted 247 days until 17 June and was equivalent to 30 
inches of liquid water on 12 April. That year also was the wettest 
on record since 1905, 48 inches of precipitation (William Knott, 
personal communication). The effect on Arphia populations is un- 
known, since we began our studies in 1964. The vagaries of climatic 
conditions of this high plateau may be an important factor in the 
maintenance of steep polymorph dines in the A . conspersa populations. 
