Hiding in plain sight: leaf beetles (Chrysomelidae: Galerucinae) use feeding damage as a masquerade decoy

• Published in: Biological journal of the Linnean Society Vol. 123; no. 2; pp. 311 - 320
• Main Authors: Konstantinov, Alexander S, Prathapan, K D, Vencl, Fredric V
• Format: Journal Article
• Language: English
• Published: UK Oxford University Press 01.02.2018
• Subjects: herbivory; predation; camouflage; defence; mimicry
• ISSN: 0024-4066; 1095-8312
• DOI: 10.1093/biolinnean/blx149

Abstract We report on a unique variant of the masquerade strategy, wherein small herbivorous leaf beetles (Chrysomelidae: Galerucinae) have recurrently evolved a close resemblance to innocuous, unprofitable decoy objects of their own manufacture, i.e. their own feeding damage. Our study is based on a worldwide sample of 119 species of leaf beetles in the subfamily Galerucinae. Most species (115) are members of the tribe Alticini, the flea beetles s.s., known for their remarkably swift jumping ability and astonishing diversity. Masquerading beetles are small, ranging in length from 1.4 to 4.2 mm, monochromatically light or dark, and lack contrasting patterns or warning colours. Although many species make shallow, light colored trenches, 53% of the adult feeding damage consists of closely spaced, oval to elongate holes that completely penetrate the host leaf, which gives it a pitted, stippled appearance. Body area was correlated with feeding hole area. Hole area increases by 0.60 mm2 for each square millimetre of beetle area. Log–linear modelling showed that beetle body colour was darker when damage was darker and lighter when damage was lighter and when host leaves were broad as opposed to narrow and were oriented horizontally as opposed to vertically. We discuss why masquerade is not a response to induced host plant defences. These findings support the hypothesis that intense selection by visually orienting predators, such as insectivorous birds, has driven small leaf beetles to evolve bodies more closely to resemble their feeding damage and evolve their feeding habits to produce damage that resembles their own bodies.