Allometry among structures of proboscises of Vanessa cardui L. (Nymphalidae) and its relationship to fluid uptake

Abstract

The morphometrics of proboscises of Vanessa cardui were examined to determine potential allometric growth relationships. Butterfly mass and six proboscis measurements were recorded from V. cardui reared on artificial diet treatments, in conjunction with fluid uptake rates. Log10 transformed data revealed negative allometry with proboscis length, butterfly mass, and drinking region length as the independent variables. Fluid uptake rates, however, had a nearly isometric relationship with most proboscis measurements, but not the total number of sensilla styloconica, which indicated inverse allometry with fluid uptake rates. The patterns exposed here show that the studied proboscis structures are important predictors for fluid uptake, but the selection pressures associated with feeding strategies and the substrates from which V. cardui feed favor a particular proboscis architecture, deviations from this configuration might require different feeding strategies and food sources.