Latitudinal gradients in ichneumonid species-richness in Australia


Dr I. D. Gauld, Department of Entomology, British Museum (Natural History), Cromwell Road, London SW7 5BD.



  • 1New data from Australia support previous suggestions that the Ichneumonidae as a whole is not more species-rich in the tropics than the group is in temperate regions.
  • 2Part of the overall lack of increase in tropical species-richness results from an absence of large groups whose sawfly hosts are not present.
  • 3In comparison with temperate faunas, a larger proportion of tropical ichneumonids are generalists, exploit pupae/prepupae, or have long ovipositors, corroborating predictions made by hypotheses advanced to explain the anomalous tropical diversity of ichneumonids.
  • 4Two large groups of pupal/prepupal parasitoids (Pimplinae and Mesostenini) are more speciose in equatorial areas.
  • 5Diurnal lepidopterous larval parasitoids, and specialist lepidopterous pupal/prepupal parasitoids are scarcer in the tropics than one might expect, but nocturnal lepidopterous larval parasitoids show an increased species-richness in the tropics. It is suggested that this may be a result of a larger proportion of the suitable host larvae being nocturnally active.