Butterfly tails change with wing size in different ways
Measurements of 223 museum butterflies found contrasting relationships between hindwing size and tail length. Some groups kept similar proportions as size increased, while others had relatively longer or shorter tails. The peer-reviewed study found no significant difference between sexes within groups. Flight and predator avoidance remain proposed explanations for the varied shapes, rather than tested functions.
Science··Night
Larger butterflies did not share one tail proportion
A peer-reviewed comparison of 223 butterflies found that tail length did not scale with hindwing size in one consistent way. In long-tailed blues and European common swallowtails, larger individuals retained proportions consistent with geometric similarity. In scarce swallowtails and purple hairstreaks, larger individuals had relatively long tails; the pattern reversed in British swallowtails. Brown hairstreaks showed no significant association between tail length and hindwing area.[1]
Museum wings provided the size comparison
The specimens came from the insect collection at Manchester Museum. Researchers used hindwing area as the size measure because preserved bodies can become distorted. They corrected tail measurements for curling during preservation, and two ways of defining the tail base gave similar results. European and British swallowtails were assessed separately because their appearance, habitat preferences and resident distributions differ. No significant sex differences in relative tail length were detected within groups.[1]
Flight and predator avoidance remain possible explanations
The authors discuss species-specific balances between flight and predator avoidance as possible explanations for the variation. The measurements did not directly test flight or attacks on living butterflies. Fragile antennae were often missing, limiting comparisons relevant to the idea that tails mimic a false head. Suitable museum material also restricted the sample, and measurement error or chance processes could contribute to variation.[1]
