Davis, Calif. 9566 Oligophagous or polyphagous insects frequently exhibit ecologically or geographically complex patterns o host-plant utilization. Such patterns have recently been documented or the butterflies Colias alexandra Edwards (Pieridae) (Ellis, I974) and Euphydryas editha Boisduval (Nyrnphalidae) (White and Singer, I974). This paper reports a similar situation among California populations o the Gray-Veined White, Pieris nail Linnaeus (Pieridae) and notes its potential significance in

more »

... nterspeciqc competition. Pieris napi is a circumpolar species; in its extensive boreal and temperate range it has been recorded on a great variety o plants o the family Cruciferae. In California it is widely distributed in (oothill 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 ar south as Yosemite, but its host preferences have been very poorly documented. In their survey o Yosemite butterflies, Garth and Tilden (I963) listed in an Appendix "some plants on which Yosemite butterflies eed as larvae." Unfortunately these records, which are mostly not attributed, do not appear to be limited to Yosemite populations. Garth and Tilden list four Crucier genera as hosts o P. napi: Barbarea (winter cress, yellow rocket), Brassica (mustard), Raphanus (radish), and Dentaria (milkmaids, crinkleroot, toothwort). O these, all but Raphanus are known hosts of P. napi in the northeastern United States. Tilden (I965) recorded P. napi in the "San Francisco Bay area" on Dentaria only.