• DOI:10.1086/283868
• Corpus ID: 34146954

The "False Head" Hypothesis: Predation and Wing Pattern Variation of Lycaenid Butterflies

@article{Robbins1981TheH,
  title={The "False Head" Hypothesis: Predation and Wing Pattern Variation of Lycaenid Butterflies},
  author={Robert K. Robbins},
  journal={The American Naturalist},
  year={1981},
  volume={118},
  pages={770 - 775}
}

• R. Robbins
• Published 1 November 1981
• Biology
• The American Naturalist

Camouflage, mimicry, and other forms of deceptive appearances have presumably evolved under selective pressures from predators who hunt by sight (e.g., Cott 1940). A fascinating example of deceptive coloration is the hypothesis that the ventral wing pattern of lycaenid butterflies (Lepidoptera: Lycaenidae) creates an impression of a head at the posterior end of the butterfly that diverts predator attacks towards the less vulnerable end of the insect (reviewed in Robbins 1980). Predators may direct their attacks towards "eyespot" markings on lepidopteran wings (Poulton 1890; Swynnerton 1926; Blest 1957), and lizards preferentially attack the "false head" of lycaenid butterflies, frequently getting a mouthful of hindwing while the butterfly escapes otherwise unharmed (Van Someren 1922). The components of wing pattern and morphology that contribute to an impression of a head, however, vary markedly among lycaenid species. Consequently, the deceptiveness of these wing patterns should vary and should be positively correlated with the frequency of deflected predator attacks. Here I present evidence confirming this correlation and supporting the hypothesis that predation influences the evolution of wing patterns among lycaenid butterflies. I then discuss possible explanations for the diversity of lycaenid wing patterns. To compare the frequency of deflected attacks with deceptiveness as predicted by the "false head" hypothesis, I used two samples of lycaenid butterflies (Eumaeini). The first sample consisted of more than 1,000 specimens of about 125 species collected on a small hill (0.5 kM2, 500 m elevation) within 5 wk at Villavicencio, Meta, Colombia. The second sample consisted of almost 400 specimens of about 75 species collected in Panama Province, Panama, during 3 mo (June-August). Every lycaenid specimen seen was chased until captured or lost. As a measure of predicted deceptiveness, I scored specimens for the following components of false-head wing patterns (fig. 1; Robbins 1980): (1) the presence of two or more contrasting lines converging, and leading a predator's eye, to the eyespot at the anal angle (caudal end) of the hindwings, (2) the occurrence of an anal angle of less than 650 as measured from the base of the hindwing to the anal lobe (end of vein Cu2) to the end of vein M1, (3) the presence of anal angle coloration contrasting with the ground coloration, and (4) the presence of tails, which presumably represent false antennae. I then placed species with all four of the above characters in rank 1, those with three characters in rank 2, those with two characters in rank 3, and those with one or zero characters in rank 4. Predators sensitive to UV radiation might see these aspects of wing patterns differently. Thus I examined 75 of these lycaenid species with a television camera modified for viewing UV wing patterns (Eisner et al. 1969), but found no differences between the UV wing pattern and the visible light wing pattern. Species placed in rank 1 have been considered classic examples of false-head