A select group of hemipterans within the suborder Auchenorrhyncha are the only animals that feed exclusively on xylem sap – a nutritionally poor liquid that exists under negative pressure within a plant's xylem vessels. To consume it, xylem-feeding bugs have evolved enlarged cibarial pumps capable of generating enormous negative pressures. A previous study examining the allometry of this feeding model suggested that small xylem feeders pay relatively higher energetic costs while feeding, favouring the evolution of larger-bodied species. However, this interspecific analysis only considered adult xylem-feeding insects and neglected the considerable intraspecific change in size that occurs across the insect's development. Here, we examine the changes in cibarial pump morphology and function that occur during the development of Philaenus spumarius, the common meadow spittlebug. We show that the cibarial pump scales largely as expected from isometry and that the maximum negative pressure is mass independent, indicating that size has no effect on the xylem-feeding capacity of juvenile spittlebugs. We conclude that a first instar nymph with a body mass 2% of the adult can still feed at the >1 MPa tension present in a plant's xylem vessels without a substantial energetic disadvantage.

Author contributions

Conceptualization: P.G.D.M.; Methodology: E.A.B., P.G.D.M.; Validation: E.A.B.; Formal analysis: E.A.B.; Investigation: E.A.B.; Data curation: E.A.B.; Writing - original draft: E.A.B., P.G.D.M.; Writing - review & editing: E.A.B., P.G.D.M.; Visualization: E.A.B.; Supervision: P.G.D.M.; Project administration: P.G.D.M.; Funding acquisition: P.G.D.M.

Funding

This work was supported by Natural Sciences and Engineering Research Council of Canada Discovery grant RGPIN-2020-07089 and Accelerator RGPAS-2020-00039 to P.G.D.M.

Data availability

The morphological data extracted from the micro-CT scans are available from figshare: https://doi.org/10.6084/m9.figshare.26012821.v1

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