1971] Willey & Willey — Populations of Grasshoppers 339 
lumber mill sites near sawdust heaps and in one case the male was 
found in an old homestead foundation. 
In 1970, populations over the entire mesa above 9200 ft crashed. 
In most areas, no Arphia could be found. In denies #5 3 a > b and 
54a, between 8 and 41 individuals were found in a total capture 
survey, about 1 to 15 percent of the expected population level. Of 
these, nearly one-half had blebs on the pronotum, an anomaly found 
in only 2% of normal populations. Lower altitude populations were 
very nearly normal in density and high counts were made of # 5°> 
51a, 82 and the North Rim of the Black Canyon National Monu- 
ment (over 600), all occurring between 7700 and 9100 ft elevation. 
Similar crashes in usually dense populations occurred 40 miles north 
at Gothic (9500 ft, Gunnison County), and Jack’s Cabin Cut-Off 
(9000 ft, Gunnison County). On the other hand, we have noted 
and collected sufficient nymphs of A. conspersa (over 200 in several 
areas) in August and September, 1970, to convince us that the 
diapausing eggs of the 1969 adult brood were not adversely affected 
by the winter and hatched normally in the summer of 1970- 
In 1971, the populations were normal in abundance, though not 
as high in number as those of 1969. The mark-recapture program on 
the Mounds (#53a) showed a population of 400, whereas in 1970 
only 15 adults were found. In September, 197 1, only one nymph 
was found in this area, two nymphs in the Burn Area (#45d, 100 
nymphs in 1970), and 16 nymphs in Pasture 5 (#54a, 41 adults in 
1970, over 200 adults in 1971). This small number of nymphs in 
1971 indicates no recovery of the 1970 brood. 
Discussion 
Black Mesa is subject to severe vagaries of weather. Since the 
snow packs of 1969-70 and 1970-71 were nearly the same length 
(216 and 215 days respectively), and the 1971 adult brood was only 
a little below normal in density, we think that conditions before the 
snowpack of 1969-70 or after it had melted probably caused the pop- 
ulation crash of 1970. These conditions could have been 1) the 
snowfall of 26 June 1969, which may have killed hatching nymphs; 
2) the wet snowfall and rains of early October, 1969, which could 
have harmed cold-immobilized nymphs; 3) the snowfall of 12 June 
1970, which could have killed emerging adults, and 4) an undetected 
late freeze which could have decimated freeze-sensitive nymphs emerg- 
ing from hibernation in May. The fact that half of the surviving 
adults had developmental anomalies, especially blebs on the prono- 
tum, indicates some sort of post-dormancy damage. However, the 
