PSYCHE 
Vol. 8 1 September-December, 1974 No. 3-4 
HOST-PLANT UTILIZATION BY PIERIS NAPI 
POPULATIONS IN CALIFORNIA 
(LEPIDOPTERA: PIERIDAE) 
By Arthur M. Shapiro 1 
Department of Zoology, University of California, 
Davis, Calif. 95616 
Oligophagous or polyphagous insects frequently exhibit ecologi- 
cally or geographically complex patterns of host-plant utilization. 
Such patterns have recently been documented for the butterflies 
Colias alexandra Edwards (Pieridae) (Ellis, 1974) and Euphydryas 
editha Boisduval (Nymphalidae) (White and Singer, 1974). This 
paper reports a similar situation among California populations of 
the Gray- Veined White, Pieris napi Linnaeus (Pieridae) and notes 
its potential significance in interspecific competition. 
Pieris napi is a circumpolar species; in its extensive boreal and 
temperate range it has been recorded on a great variety df plants of 
the family Cruciferae. In California it is widely distributed in 
foothill and lower montane (Yellow Pine-Incense Cedar-Douglas 
Fir) environments in the Coast Ranges south to San Luis Obispo 
County and in the Sierra Nevada at least as far south as Yosemite, 
but its host preferences have been very poorly documented. In their 
survey of Yosemite butterflies, Garth and Tilden (1963) listed in 
an Appendix “some plants on which Yosemite butterflies feed as 
larvae.” Unfortunately these records, which are mostly not at- 
tributed, do not appear to be limited to Yosemite populations. Garth 
and Tilden list four Crucifer genera as hosts of P. napi: Barbarea 
(winter cress, yellow rocket), Brassica (mustard), Raphanus (rad- 
ish), and Dentaria (milkmaids, crinkleroot, toothwort). Of these, 
all but Raphanus are known hosts of P. napi in the northeastern 
United States. Tilden (1965) recorded P. napi in the “San Fran- 
cisco Bay area” on Dentaria only. 
This research was financed in part by grant D-804 from the Committee 
on Research of the Academic Senate, U.C. Davis. 
Manuscript received by the editor August 16, 1974. 
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