A Tropical Hawkmoth Community: Costa Rican Dry Forest Sphingidae

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Abstract
Hawkmoths (Sphingidae) constitute a major class of pollinators in the lowland dry forest of Costa Rica. In our study area, hawkmoths are the primary pollinators of about 10 percent of the tree species; they also pollinate various species of shrubs, herbs, lianas, and epiphytes. We found a total of 65 hawkmoth species and 31 native plant species that were adapted primarily for hawkmoth pollination. Abundance of both hawkmoths and hawkmoth flowers peaked in the first half of the wet season (May-July). Numbers of hawkmoths decreased through the dry season (December to April) with lowest numbers during April. Species of hawkmoth flowers also decreased through the dry season, but several species began flowering before the onset of the wet season and before the sudden increase in hawkmoth numbers that followed shortly after the first rains. Tube lengths of hawkmoth flowers ranged from 0 to 19 cm (.hivin.x = 5.1 cm), marched by the range in length of hawkmoth tongues (1-20 cm, .hivin.x = 4.9 cm). Hawkmoth tongue lengths were correlated with body size (wing length) (r = .70). Long flower tubes restricted access to nectar to long-tongued moths. However, long-tongued moths did not restrict their visits to long-tubed flowers. In fact, hawkmoths visited many species of flowers adapted for other pollinator types-e.g., hummingbirds, bees, and bats-along with hawkmoths flowers whose tubes were much shorter than their tongue lengths. The attractiveness of hawkmoths flower species varied greatly: some flowers were always heavily visited, other species were virtually ignored. In less attractive flowers, nectar accumulated during the night and attracted a variety of diurnal visitors the following morning. Similarly, hawkmoth flowers that opened before dark attracted diurnal and crepuscular visitors (bees, wasps, hummingbirds, butterflies) that robbed nectar and pollen, possibly decreasing flower attractiveness to hawkmoths.