445 THE RAFFLES BULLETIN OF ZOOLOGY 2008 FEEDING PREFERENCES OF PHASMIDS (INSECTA: PHASMIDA) IN A BORNEAN DIPTEROCARP FOREST Robert R. Junker Department of Animal Ecology and Tropical Biology, Biozentrum, University of Würzburg, 97074 Würzburg, Germany Email: r.junker@biozentrum.uni-wuerzburg.de Takao Itioka Graduate School of Human and Environmental Studies, Kyoto University, Sakyo, Kyoto 606-8501, Japan. Email: itioka@mbox.kudpc.kyoto-u.ac.jp Phil E. Bragg 8, The Lane, Awsworth, Nottinghamshire, NG16 2QP, U.K. Nico Blüthgen Department of Animal Ecology and Tropical Biology, Biozentrum, University of Würzburg, 97074 Würzburg, Germany Email: bluethgen@biozentrum.uni-wuerzburg.de (Corresponding author) ABSTRACT. – Stick and leaf insects (Phasmida) representing 19 species (53 individuals) were collected in a lowland dipterocarp forest (Lambir Hills, Sarawak, Malaysia). Dual-choice tests were conducted to examine whether phasmids discriminate between young and old leaves of seven plant species. A second set of tests examined the preferences of phasmids for leaves from Dryobalanops lanceolata (Dipterocarpaceae) saplings versus leaves from the upper canopy of the same tree species. Haaniella echinata and other flightless species (Heteropterygidae and Lonchodinae) fed on nearly all plant species offered and showed significant preferences for old leaves in three plant species. In contrast, flying phasmids (Ashiphasmatinae and Necrosciinae) rejected leaves from most plants and did not show consistent leaf age choices. H. echinata and flightless phasmids preferred canopy leaves from D. lanceolata over leaves from saplings, regardless of leaf age. Our results are consistent with the hypothesis that young leaves of some plant species are better defended against generalist herbivores than old leaves and that saplings are better defended than adult trees. Since upper canopy leaves were highly palatable to understorey phasmids, factors other than chemical defences must contribute to the low abundance of phasmids in forest canopies. KEY WORDS. – Dryobalanops lanceolata, forest canopy, Haaniella echinata, herbivory, leaf age, lowland rainforest. RAFFLES BULLETIN OF ZOOLOGY 2008 56(2): 445–452 Date of Publication: 31 Aug.2008 © National University of Singapore INTRODUCTION In virtually all ecosystems, herbivorous insects constitute a large proportion of the animal species and consume foliage, plant sap, or other plant parts from nearly the entire flora. The diversity of insect herbivores is highest in tropical rainforests (Novotny et al., 2004). Woody plants in tropical forests are more damaged by herbivores than those from temperate forests (Coley & Barone, 1996), but this increased damage is not necessarily accompanied by a higher density of herbivore individuals (Novotny et al., 2006). Comparative surveys on food plant selection of tropical herbivore communities have begun to unravel their actual host plant ranges and preferences (Basset, 1996; Barone, 1998; Basset, 1999; Novotny & Basset, 2005; Novotny et al., 2006). While many beetles and butterfly caterpillars are plant genus specialists, orthopteroids are often polyphagous (Novotny et al., 2002). However, for most species the natural host range is unknown. Few studies have compared the host plant selection of rainforest orthopteroid communities (e.g. grasshoppers, Rowell, 1978), including Phasmida (Tay & Seow-Choen, 1996; Novotny et al., 2002; Blüthgen et al., 2006). Phasmids and other orthopteroids such as katydids are usually less numerous than several other tropical insect taxa, particularly in comparison to the large holometabolous orders (Coleoptera, Diptera, Hymenoptera and Lepidoptera). In canopy samples from Southeast Asian rainforests, orthopteroids typically contributed less than 3% of the arthropod individuals (Stork, 1987; Stork & Brendell,