1952] 
Remington — Nearctic Lepidoptera 
65 
were on the underside of leaves; five were on the lower sur- 
face of large seed-silicles. Thirty of these ova were present 
singly on leaves or silicles ; there were two ova on each 
of twelve leaves and one silicle (once one ovum was laid 
on top of the other) ; one leaf bore three ova. It was not 
possible to determine how often two or three ova were laid 
at a single visit of a female, but on 5 July I actually saw 
the female lay two ova side by side on certain leaves. At 
Rabbit Ears Pass, Routt Co., Colo., on 15 July, Jeanne E. 
Remington saw a napi female lay several ova on Arabis 
drummondi Gray [R.C.R.]. In Europe P. napi has been 
reared on plants of at least seven genera of Cruciferae 
(including Sisymbrium), but in Coos Co., New Hampshire, 
the basic, if not exclusive, food is Dentaria, according to 
information received from Donald J. Lennox. 
7. Colias eurytheme Bdv. This name is used here for 
all orange members of the eurytheme-philodice complex of 
North America. The pure yellow individuals ( philodice ) 
are not common in the mountains in Boulder County, but 
observations suggest that they are permanent residents 
and survive the winter up to high altitudes. As the season 
progresses, huge orange individuals ( eurytheme ) begin 
to appear and increase in numbers for some weeks. There 
is clearly some hybridizing with philodice, as in all other 
regions where the two species are sympatric; I have a 
small series from Boulder County taken in 1949 above 
8,000', which includes two males and one female of philodice, 
three males and eight females of “pure” eurytheme, two 
females which look like my laboratory backcrosses to 
eurytheme, one female like my experimental Fi hybrids, 
and three white females not certainly placeable. The 
determination of foodplants of these two species of Colias 
in any locality is of great interest, so it is regrettable 
that the following records are so scanty. On 6 July 
1949 a “pure” eurytheme female was seen ovipositing on 
Thermopsis montana Nutt. [R.C.R.]. Six days later at 
Nederland a female eurytheme laid several ova on the up- 
perside of leaves of an Astragalus which Dr. Rollins ten- 
tatively identified as u racemosus Pursh.?” (fruit was not 
collected) . 
