Coherent array of branched filamentary scales along the wing margin of a small moth
In butterflies and moths, the wing margins are fringed with specialized scales that are typically longer than common scales. In the hindwings of some small moths, the posterior margins are fringed with particularly long filamentary scales. Despite the small size of these moth wings, these scales are much longer than those of large moths and butterflies. In the current study, photography of the tethered flight of a small moth, Phthorimaea operculella, revealed a wide array composed of a large number of long filamentary scales. This array did not become disheveled in flight, maintaining a coherent sheet-like structure during wingbeat. Examination of the morphology of individual scales revealed that each filamentary scale consists of a proximal stalk and distal branches. Moreover, not only long scales but also shorter scales of various lengths were found to coexist in each small section of the wing margin. Scale branches were ubiquitously and densely distributed within the scale array to form a mesh-like architecture similar to a nonwoven fabric. We propose that possible mechanical interactions among branched filamentary scales, mediated by these branches, may contribute to maintaining a coherent sheet-like structure of the scale array during wingbeat.
KeywordsSmall moth Wing margin Branched filamentary scale Mesh-like architecture Coherence
We thank Dr. Hisao Honda and the anonymous reviewers for their valuable comments on the manuscript. This study was supported by the EM facility at the National Institute for Physiological Science (Okazaki, Japan).
- Allyn AC, Rothschild M, Smith DS (1982) Microstructure of blue/green and yellow wing membranes in lepidoptera. With remarks concerning the function of pterobilins. 1. Genus Graphium. Bull Allyn Mus 75:1–19Google Scholar
- Brodsky AK (1994) The evolution of insect flight. Oxford University Press, New YorkGoogle Scholar
- Downey JC, Allyn AC (1975) Wing-scale morphology and nomenclature. Bull Allyn Mus 31:1–32Google Scholar
- Ghiradella H (1998) Hairs, bristles, and scales. In: Locke M (ed) Microscopic anatomy of invertebrate. Volume 11A: Insecta. Hoboken, John Wiley and Sons, pp 257–287Google Scholar
- Hirata K, Kubota T (1957) Microstructure of the scale of butterfly, Colias erate poliographus Motschulsky, elucidated by electron microscopy. Sci Rep Kagoshima Univ 6:151–167Google Scholar
- Kozlov MV, Iranov VD, Grodnitsky DL (1986) Evolution of the wing apparatus and wing kinematics in Lepidoptera. Usephi sovr biol 101:291–305 (In Russian)Google Scholar
- Nijout HF (1991) The development and evolution of butterfly wing patterns. Smithsonian Inst Press, WashingtonGoogle Scholar
- Sugimoto M, Saigusa T (2002) Baeotia-like genus of the family Psychidae (Lepidoptera) from Taiwan, with a discussion on its systematic position. Trans Lepid Soc Japan 53:215–224Google Scholar
- Weis-Fogh T (1973) Quick estimates of flight fitness in hovering animals, including novel mechanisms for lift production. J Exp Biol 59:169–230Google Scholar
- Wooton RJ (1993) Leading edge section and asymmetric twisting in the wings of flying butterflies (Insecta, Papilionoidea). J Exp Biol 180:105–117Google Scholar