The effects of density and relative size on the aggressive behaviour, movement and feeding of damselfly larvae (Odonata: Coenagrionidae)

Mark A. McPeek, Philip H. Crowley

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65 Scopus citations


How the aggressive behaviour of the larvae of a damselfly species, Ischnura verticalis, changed when density and size combinations were manipulated, and whether changes in feeding and movement patterns accompanied changes in aggressive behaviour were investigated in the laboratory. During aggressive encounters larvae struck with their mouthparts at larvae of the same size as themselves more frequently as density increased. However, proportionately fewer encounters occurred between larvae of the same size as density increased and as the size of individuals present, but not involved in the encounter, increased within the highest density. Density did not affect the behaviour used to initiate encounters by larger or smaller larvae, but both larger and smaller larvae initiated proportionately fewer encounters as density increased. All instars decreased their movement and responsiveness toward prey as larval density was increased and when paired with successively larger instars within each density. However, only the two larger instars decreased the amount of prey they consumed in response to the manipulations. Larvae appeared to reduce their involvement in aggressive encounters by increasing their vigilance of other larvae. The potential population consequences of these alterations in individual behaviour are discussed.

Original languageEnglish
Pages (from-to)1051-1061
Number of pages11
JournalAnimal Behaviour
Issue number4
StatePublished - Aug 1987

Bibliographical note

Funding Information:
The work presented here represents part of an M.S. thesis project completed by the senior author and directed by the junior author. Several people contributed valuable ideas and comments during the project, including Dan Johnson, Richard Krys-cio, David Prior, Andy Sih and Kevin Strohmeier. Thorough and helpful critiques of the thesis were provided by John Just and William McComb. Previous drafts of the manuscript unleashed con- structive criticism from Robert Baker, Pat Dillon, Don Hall, Michael Jefferies, Dan Johnson, John Lawton, Mary Linton, Jerry Nagel, Kevin Stroh-meier, Earl Werner and two anonymous reviewers. We thank them all, and we gratefully acknowledge support from an NSF Graduate Fellowship to MAM and NSF grants DEB-8104424 and BSR-8400377 to PHC.

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology


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