Large Hind Wings Enhance Gliding Performance in Ground Effect in a Neotropical Butterfly (Lepidoptera: Nymphalidae)

摘要

Neotropical butterflies in the nymphalid genera Pierella Herrich-Schaffer, 1865 (Lepidoptera, Nymphalidae) and Cithaerias Hubner, 1819 (Lepidoptera, Nymphalidae) are known to glide near ground level, and have a high forewing aspect ratio.The hind wings of Pierella are proportionately larger than those of Cithaerias, suggesting a potential role in gliding flight. We show that Pierella helvina (Hewitson, 1860) (Lepidoptera, Nymphalidae) is capable of gliding for longer periods of time than Cithaerias pireta (Stoll, 1780) (Lepidoptera, Nymphalidae) both in the field and a laboratory setting. Experimental reduction of hind wing area in P. helvina led to a decrease in male gliding performance, and an increase in female wing-beat frequency. We also found that escape velocity decreased in both sexes after hind wing area reduction, but the effect was strongest in females. Although the increased drag associated with large hind wings could be detrimental to gliding flight, the large hind wing area of P. helvina effectively enhances gliding performance in ground effect.This study is the first to investigate the role of hind wings on butterfly gliding performance.