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Video Q&A ViewAttendees 1

Plant-Insect Ecosystems

10-Minute Paper

P-IE: Ecology On-Demand Presentations

Seasonal differences in pupal survival of a common North American butterfly

On-Demand
On-Demand

    Presenting Author(s)

  • Martha Weiss

    Professor
    Georgetown University
    Washington, District of Columbia

    • Co-Author(s)

  • AB

    Allison Brackley

    Georgetown University
    Washington, District of Columbia

  • JL

    John Lill

    The George Washington University
    Washington, District of Columbia

All holometabolous insects undergo a pupal life stage, a transformative period during which most pupae are immobile and unable to flee from natural enemies or harmful abiotic conditions.  For multivoltine species with both diapausing and non-diapausing generations, each experiencing different ecological challenges, pupal mortality is likely to vary across seasons.

Early-season generations of Epargyreus clarus (Hesperiidae), a native North American butterfly, produce continuously developing pupae while late-season generations produce diapausing pupae. We conducted a set of field experiments to investigate variation in pupal survival across the year (comparing non-diapausing and diapausing pupae). 

Surprisingly, during the relatively short (10-14 day) summer pupal duration, daily per capita mortality rate (5% ± 1.6 SD) was an order of magnitude higher than that of diapausing (winter) pupae (0.3% ± 6-3 SD), despite a nearly 20-fold longer pupal duration recorded for the latter. Survival curves from two winter field experiments and three summer field experiments were similar within each seasonal category. We attribute the increased pupal mortality for the summer cohorts to higher mammalian predation during the warmer months.

Our results provide some of the first illustrations of the importance of seasonality in determining pupal survival, and add to our understanding of this neglected yet essential stage of the lepidopteran life cycle.