Latitudinal gradients in ichneumonid species‐richness in Australia

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Abstract
New 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. Part of the overall lack of increase in tropical species‐richness results from an absence of large groups whose sawfly hosts are not present. In 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. Two large groups of pupal/prepupal parasitoids (Pimplinae and Mesostenini) are more speciose in equatorial areas. Diurnal 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.