42 
Psyche 
[Vol. 92 
The choice tests were conducted in a small petri dish (6 cm diame- 
ter) lined with a piece of damp filter paper. Because E. colon and E. 
chalcedona are batch layers and the pre-diapause larvae are gregar- 
ious, the tests were conducted with groups of larvae. For each test, a 
group of 10 larvae was given a 5 mm disc of P. breviflorus and one 
of S. albus. These discs were punched out of the leaf with a cork 
borer, just prior to the beginning of each test. The discs were placed 
in the center of the petri dish about 1 mm apart, the larvae intro- 
duced, and allowed to feed for 48 hours. At 24 and 48 hours, the 
amounts of the two leaf discs eaten were estimated visually to the 
nearest ten percent (Jermy, et al., 1964; Bowers, 1979). 
Results 
For each of the intraspecific crosses, the newly hatched larvae 
significantly preferred their own hostplant (Table 1, Fig. 1). In con- 
trast, the hybrid larvae showed no preference for either plant (Table 
1, Fig. 1). This ostensible lack of preference by the hybrid larvae, 
however, was not due to each group of larvae eating approximately 
equal amounts of both plant species, nor was it due to some larvae 
within a group feeding on the disc from one species and others on 
the other. On the contrary, each group of hybrid larvae appeared to 
0 
tr 
UJ 
1 
z 
0-20 21-40 41-60 61-80 81-100 0-20 21-40 41 -60 61-80 81*100 0*20 21-40 41*60 61*80 81-100 
AMOUNT P BREVIFLORUS EATEN AS % OF TOTAL EATEN 
Fig. 1. The amount of Penstenion breviflorus eaten by E. chalcedona (CH X 
CH), E. colon (ST X ST) and the hybrids (CH X ST). The amount of P. breviflorus 
eaten is shown as the percent of the total amount eaten of both plant species. 
