PSYCHE 
Vol. 86 
March, 1979 
No. 1 
THE PHENOLOGY OF PIERIS NAP/ MICROSTRIATA 
(LEP1DOPTERA: PIERIDAE) DURING AND AFTER 
THE 1975-77 CALIFORNIA DROUGHT, AND ITS 
EVOLUTIONARY SIGNIFICANCE* 
By Arthur M. Shapiro 
Department of Zoology, 
University of California, 
Davis, California 95616, U.S.A. 
Introduction 
Interest in the theoretical basis of insect phenology has increased 
very markedly in recent years (Bradshaw, 1974; Cohen, 1970; Giesel, 
1976; Levins, 1969). The evolution of phenological “strategies” via 
natural selection is of interest to ecologists and applied entomolo¬ 
gists alike. Insect phenology involves responses to both “normal” 
and “abnormal” weather. The developmental plasticity displayed by 
a population may determine its survival in seasons of unusual mete¬ 
orological stress and in turn may reflect a history of selection by 
recurrent exposure to that stress. 
The 1975-77 California drought was a short-term climatic anom¬ 
aly with no equal in the meteorological records of that state. Any 
event of such magnitude would be expected to affect both phenol¬ 
ogy and reproductive success of a great variety of organisms, espe¬ 
cially annual or ephemeral species. Since' 1972 the phenology of 
entire butterfly faunas has been monitored along a transect parallel¬ 
ing Interstate Highway 80 from sea level at Suisun Bay to 2750 m at 
Castle Peak, north-central California. This has permitted year-to- 
year comparisons within localities as well as within-year compari¬ 
sons among localities. This long-term study involving over 150 
species includes the 1975-77 drought and the tremendous rains of 
winter 1977/78. Certain butterfly populations showed very pro- 
* Manuscript received by the editor June 30, 1979. 
