Breaking Haller's rule: brain-body size isometry in a minute parasitic wasp.

E. van der Woude, H.M. Smid, L. Chittka, M.E. Huigens

Research output: Contribution to journalArticleAcademicpeer-review

34 Citations (Scopus)


Throughout the animal kingdom, Haller's rule holds that smaller individuals have larger brains relative to their body than larger-bodied individuals. Such brain-body size allometry is documented for all animals studied to date, ranging from small ants to the largest mammals. However, through experimental induction of natural variation in body size, and 3-D reconstruction of brain and body volume, we here show an isometric brain-body size relationship in adults of one of the smallest insect species on Earth, the parasitic wasp Trichogramma evanescens. The relative brain volume constitutes on average 8.2% of the total body volume. Brain-body size isometry may be typical for the smallest species with a rich behavioural and cognitive repertoire: a further increase in expensive brain tissue relative to body size would be too costly in terms of energy expenditure. This novel brain scaling strategy suggests a hitherto unknown flexibility in neuronal architecture and brain modularity.
Original languageEnglish
Pages (from-to)86-92
JournalBrain, behavior and evolution
Issue number2
Publication statusPublished - 2013


  • trichogramma-brassicae
  • cotesia-glomerata
  • miniaturization
  • allometry
  • insects
  • evolution
  • parthenogenesis
  • coleoptera
  • ptiliidae
  • rubecula

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