Abstract
This paper describes a novel method of measuring host specificity and determining host rank order. As applied to oviposition behavior of the butterfly Euphydryas editha, the rank order of preference is the order in which plants become acceptable as the insect searches, while specificity is quantified in terms of the rate at which searching insects become less discriminating. The information obtained is different from that gleaned from other preference testing techniques. It is useful in helping to assess the behavioral bases of interpopulation differences in the degree of host specialization, in understanding the ways in which multiple host use is generated within a population, and in testing hypotheses about the evolution of host specialization. The data presented here show interpopulation variation in both rank order of host species and in the degree of host specificity of E. editha.