Behavioral plasticity of a grass-feeding caterpillar in response to spiny- or smooth-edged leaf blades

Craig P. Keathley, Daniel A. Potter

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Ontogenetic changes in feeding behavior of armyworms, Pseudaletia unipucta (Haworth), were compared on tall fescue [Schedonorus arundinaceus (Schreb.) Dumort] cultivars with spiny-, intermediate-, or smooth-edged leaf blades to clarify whether the edge spines deter caterpillars, in which case release of modified, smooth-edged forage grasses for improved livestock performance might aggravate armyworm damage to pastures. Edge biting, success initiating edge-feeding, and propensity to window- or edge-feed were observed for individual 2nd, 3rd, or 4th instars on grass leaf blades with intact margins. Early second instars bit smooth and spiny leaf edges with equal frequency but were unable to initiate edge-feeding. They fed on leaf edges after margins were cut away, but not when leaf juice was applied to intact edges, indicating the leaf margin is a barrier. Third and 4th instars mostly edge-fed on smooth leaves, but on the grasses with spiny margins they compensated for the difficulty of edge-feeding by prolonging their window-feeding. There was no developmental cost to window-feeding by 3rd instars, but 4th instars suffered reduced weight gain on spiny grass apparently because, unlike earlier instars, their mandibles are too large and not well shaped for efficient window-feeding between the parallel vascular bundles. Armyworms display behavioral plasticity in feeding mode in response to spiny- versus smooth-edged grasses. Greater use of smooth-bladed pasture grasses may result in proportionately more edge-feeding by armyworms but is unlikely to result in markedly greater pasture losses because this grass-feeding specialist so effectively exploits conventional tall fescue despite its structural characteristics.

Original languageEnglish
Pages (from-to)339-349
Number of pages11
JournalArthropod-Plant Interactions
Issue number4
StatePublished - Dec 2011

Bibliographical note

Funding Information:
Acknowledgments We thank C. Redmond, E. Dobbs, C. Elder, J. Houle, V. Jacquier, and E. Avet for technical assistance, T. Phillips for advice selecting grass cultivars, D. Brown for advice establishing grasses, M. Sharkey and S. Clutts for assistance with microscope photography, D. Yu for electron microscope training, and A. Boring for wasp identification. This work was supported by USDA FAPRU grant number 6440-21000-001-00. This is paper number 10-08-131 of the Kentucky Agricultural Experiment Station.


  • Armyworm
  • Feeding plasticity
  • Ontogenetic changes
  • Spinescence
  • Tall fescue

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology
  • Agronomy and Crop Science
  • Insect Science


Dive into the research topics of 'Behavioral plasticity of a grass-feeding caterpillar in response to spiny- or smooth-edged leaf blades'. Together they form a unique fingerprint.

Cite this