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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. [ABSTRACT FROM AUTHOR]

The structure and functionality of the reduced proboscis of males of P. strigataria was studied. Scanning electron microscopy revealed a proboscis structurally similar to functional proboscises of other lepidopteran species, including chemo- and mechanosensilla and a tip-region with larger spaces between the dorsal legulae. Drops of red food coloring applied to the dorsal legulae entered the proboscis. Subsequent dissections exposed a complete and functional gut containing food coloring. We suggest that Lepidoptera with reduced proboscises might rely on capillarity as an initial step for fluid to enter the proboscis for subsequent uptake. Field observations are needed to determine if P. strigataria, and other Lepidoptera with reduced proboscises, feed in their natural habitats. [ABSTRACT FROM AUTHOR]