Abstract
Estimating the survivorship of lepidopteran larvae in the field poses many problems, most notably the potential for monitored subjects to simply wander away. Larvae of the family Hesperiidae, however, construct and dwell in shelters built out of leaf tissue on their host plants, return to their shelters between feeding bouts, and build a predictable series of shelters during larval ontogeny. Here we describe the shelter building behavior of Pyrrhopyge papius Hopffer, 1874 from northeastern Ecuador. Subsequently we test the use of the Mayfield method, a widely-used ornitho- logical method for estimating survivorship of nests, to examine its utility for monitoring survival in free-living hesperiid larvae. Pyrrhopyge papius builds three distinct shelter types during its ontogeny. Monitoring of larvae in the field was successful, generating a predicted 16.4% survivorship from hatching to pupation. We found no significant differences in survivorship between larval shelter types, and only marginally significant differences between years. The Mayfield method of data collection and analysis may be a useful tool for some studies of survivorship in free-living lepidopteran larvae.
Highlights
What has become known as the Mayfield method is a simple tool, widely employed by ornithologists to estimate survivorship of bird nests (e.g. GREENEY & HALUPKA 2008, WANLESS & HOCKEY 2008, KHOURY et al 2009)
We found no significant differences in survivorship between larval shelter types, and only marginally significant differences between years
The relative role of predation in larval lepidopteran life tables is, often difficult to ascertain due to the difficulty of monitoring mobile life stages in the field and the uncertainty posed by the complete disappearance of larvae which may have variously either fallen from the plant, wandered away, or been removed by a predator
Summary
What has become known as the Mayfield method is a simple tool, widely employed by ornithologists to estimate survivorship of bird nests (e.g. GREENEY & HALUPKA 2008, WANLESS & HOCKEY 2008, KHOURY et al 2009). Mayfield proposed that nest survivorship should be evaluated based on the probability that any given nest would survive one more day using the equation 1 – [(number of failed nests)/(total exposure days)]. Once the probability that a nest will survive one more day is known, the estimate is raised to the power of the total number of days in the nesting cycle (i.e., from laying the eggs to fledging of the young). This model makes the assumption that daily nest survival is constant in time. We document ontogenetic changes in larval shelter construction of a common skipper in the eastern Andes of Ecuador, Pyrrhopyge papius papius Hopffer, 1874, and test the application of the Mayfield method for estimating larval survivorship in the field
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