Delayed population explosion of an introduced butterfly.

1. The causes of lagged population and geographical range expansions after species introductions are poorly understood, and there are relatively few detailed case studies. 2.

Ecological determinants of food plant choice in the checkerspot butterfly Euphydryas editha in Colorado.

The larvae of Euphydryas editha in Gunnison County, Colorado, feed on Castilleja linariifolia. Two related plants, C. chromosa and Penstemon strictus, occur in the same area and are equally nutritious, but are not eaten.

Long range dispersal in checkerspot butterflies: Transplant experiments with Euphydryas gillettii.

Transfers of eggs and larvae from montane Wyoming populations of Euphydryas gillettii south to locations in the central Colorado mountains have resulted in the establishment of at least one Colorado population. This result shows that the previous absence of the species from Colorado was the result of its inability to cross the barrier of the Wyoming Basin, not the ecological unsuitability of Colorado habitats. This, in turn, supports the contention that Euphydryas do not easily disperse long distances.