Male indifference to female traits in an arctiid moth (Utetheisa ornatrix)

Abstract.  1. Female Utetheisa ornatrix (Lepidoptera: Arctiidae) mate selectively with large males able to transmit sizeable quantities of nutrient and defensive pyrrolizidine alkaloid with the spermatophore. The female gauges male size indirectly by assessment of the male's courtship pheromone. 2. Male Utetheisa invest upward of 10% of body mass in spermatophore production, and could therefore have been expected to be choosy; however, when offered females differing in alkaloid content, body mass, or mating status, males showed disregard of these parameters, both in their choice of partner and in their allocation of resources to the spermatophore. 3. It is concluded that Utetheisa males do not have the option to select females by comparison shopping. Females broadcast their attractant pheromone for less than an hour per day. Given this time constraint and the potentially high cost of mate localisation, males may have no choice but to mate on an opportunistic basis.