Insect Inhabitants of Fruits of Leptospermum, Eucalyptus and Casuarina in Southeastern Australia

Abstract

Insects dissected and reared from the fruits of four species of Leptospermum (myrsinoides, juniperinum, laevigatum and lanigerum), three species of Eucalyptus (baxteri, obliqua and willisil] and four species of Casuarina (pusilla, stricta, littoralis and paludosa), collected from 18 sites over four seasons at Wilsons Promontory in south-eastern Australia, are enumerated and discussed. Fruits of all species supported abundant and diverse assemblages of seed-eating insects and associated parasites. The distribution of phytophagous insects was related to host-plant phylogeny and, in particular, to fruit morphology. When fruit morphology was relatively constant within a host-plant genus (Eucalyptus and Casuarina), that genus supported a characteristic suite of seed-eating insects; when it varied markedly between species (Leptospermum), so did the composition of seed-eating insects. Insect species often occurred widely within a host genus, but were never recorded from different host genera. An extensive radiation of seed-eating Anobiidae (Dryophilodes spp.) in myrtaceous capsules parallels that of weevils known in fruits of Acacia. The major seed-eating insects recorded in each host taxon were: (a) in Eucalyptus spp. (all fruits woody and persistent capsules), Dryophilodes sp. B (Coleoptera : Anobiidae) and chalcidoid wasps, mostly Megastigmus sp. (Torymidae) and Eurytoma sp. (Eurytomidae); (b) in Casuarina spp. (all fruits woody and persistent 'cones'), chalcidoid wasps, mostly Bootanelleus sp. (Torymidae), and unidentified cosmopterigid moths; (c) in Leptospermum juniperinum and L. lanigerum (woody and persistent capsules), Dryophilodes spp. C and D, and unidentified cosmopterigid moths; (d) in L. laevigatum (semi-fleshy and semi-persistent capsules), Dryophilodes sp. E and an unidentified cecidomyiid fly; (e) in L. myrsinoides (fleshy and ephemeral capsules), an unidentified weevil and unidentified carposinid moth.