1985] 
Bowers — Euphydryas 
41 
considered a single species (McDunnough, 1927; Gunder, 1929; dos 
Passos, 1964; Scott, 1980). The hostplants used by the Euphydryas 
populations that I studied are in different families: the E. colon 
population uses primarily Symphoricarpos albus in the Caprifolia- 
ceae, while the E. chalcedona population feeds primarily on Pen- 
stemon breviflorus in the Scrophulariaceae. I compared the 
hostplant choice of neonate larvae of E. chalcedona, E. colon, and 
the hybrids. 
Materials and Methods 
Euphydryas colon larvae were collected from a population at 
Satus Pass (ST) in Yakima County, Washington. In this population, 
larvae feed primarily on Symphoricarpos albus (Caprifoliaceae), 
although postdiapause larvae may occasionally be found feeding on 
Penstemon sp. (Scrophulariaceae). Both of these plant genera con- 
tain iridoid glycosides (Bowers, unpublished; Kooiman, 1970; 
Jensen, et al., 1974). Penstemon sp. and 5. albus grow close to each 
other in this population. 
Euphydryas chalcedona larvae were from a population north of 
Chico, on Crown Point Road (CPR), Butte County, California. The 
primary hostplant used in this population is Penstemon breviflorus 
(Scrophulariaceae). Oviposition and pre-diapause larval feeding are 
confined to this plant species; however post-diapause larvae may be 
found feeding on Castilleja sp. and/or Diplacus bifidus (Scrophula- 
riaceae). These species all contain iridoid glycosides (Kooiman, 
1970; Jensen, et al., 1975; Bowers, unpublished). 
The post-diapause larvae collected from these populations, were 
brought back to Stanford University, and reared to the adult stage 
on leaves of S. albus (E. colon ) or P. breviflorus (E. chalcedona). 
Adults were mated in net bags hung in a sunny window. For ovipo- 
sition, mated females were put into glass cylinders covered with 
netting and containing a sprig of the appropriate hostplant. There 
appeared to be no problems in getting E. colon and E. chalcedona to 
hybridize in the laboratory, and a high proportion of the hybrid 
eggs were viable (Bowers, unpublished). 
Egg masses were removed from the leaf on which they had been 
laid and kept in a growth chamber at 25 C Day:20 C Night, and a 
photoperiod of 16L:8D. When the larvae hatched, they were im- 
mediately given a choice test. 
