Attack risk for butterflies changes with eyespot number and size

Area of Science:

• Ecology
• Evolutionary Biology
• Animal Behavior

Background:

• Butterfly eyespots are theorized to function in predator deflection or intimidation.
• The specific factors influencing which function eyespots serve remain unclear.
• Previous studies show variation in eyespot size, number, and wing size across species, complicating survival analysis.

Purpose of the Study:

• To investigate how individual factors (eyespot size, number, wing size) contribute to butterfly eyespot function.
• To determine the impact of different eyespot configurations on predator avoidance and survival.

Main Methods:

• Utilized paper butterfly models with systematically varied eyespot characteristics (size, number).
• Exposed models to natural predation scenarios in the field to record interactions.
• Measured eyespot size across 255 species within the Nymphalidae family.
• Mapped eyespot size distribution onto the Nymphalidae phylogenetic tree.

Main Results:

• Single, large eyespots ( > 6 mm diameter) significantly reduced predation.
• Multiple, small eyespots led to increased predation rates.
• Large eyespots were found to be rare, predominantly on ventral wing surfaces.
• Phylogenetic analysis indicated a dispersed distribution of large eyespots across Nymphalidae lineages.

Conclusions:

• Single large eyespots appear to function in predator intimidation, enhancing survival.
• Multiple small eyespots may act as conspicuous signals but lack intimidation value.
• Eyespot size, particularly large size, may be a key evolutionary trait for predator deterrence.
• The distribution of large eyespots suggests convergent evolution rather than strict phylogenetic inheritance.