The diversity of beetle assemblages in different habitat types in Sabah, Malaysia.

The diversity of beetle assemblages in different habitat types (primary forest, logged forest, acacia plantation and oil palm plantation) in Sabah, Malaysia was investigated using three different methods based on habitat levels (Winkler sampling, flight-interception-trapping and mist-blowing). The overall diversity was extremely high, with 1711 species recorded from only 8028 individuals and 81 families (115 family and subfamily groups). Different degrees of environmental changes had varying effects on the beetle species richness and abundance, with oil palm plantation assemblage being most severely affected, followed by acacia plantation and then logged forest. A few species became numerically dominant in the oil palm plantation. In terms of beetle species composition, the acacia fauna showed much similarity with the logged forest fauna, and the oil palm fauna was very different from the rest. The effects of environmental variables (number of plant species, sapling and tree densities, amount of leaf litter, ground cover, canopy cover, soil pH and compaction) on the beetle assemblage were also investigated. Leaf litter correlated with species richness, abundance and composition of subterranean beetles. Plant species richness, tree and sapling densities correlated with species richness, abundance and composition of understorey beetles while ground cover correlated only with the species richness and abundance of these beetles. Canopy cover correlated only with arboreal beetles. In trophic structure, predators represented more than 40% of the species and individuals. Environmental changes affected the trophic structure with proportionally more herbivores (abundance) but fewer predators (species richness and abundance) in the oil palm plantation. Biodiversity, conservation and practical aspects of pest management were also highlighted in this study.

Relationships betweenDendroctonus micans Kug. (Coleoptera: Scolytidae) survival and development and biochemical changes in Norway Spruce,Picea abies (L.) Karst., phloem caused by mechanical wounding.

The bark of Norway spruce trees,Picea abies (L.) Karst., was wounded to produce areas of bark with differing biochemical characteristics. Adults and larvae ofDendroctonus micans Kug. were inserted into these trees at points around the wounds. Larval survival was higher, larval dry weights were higher, and adults were more likely to oviposit at sites around the wound that had higher phloem moisture contents. Larvae showed higher survival and dry weights in phloem with low terpene contents. Adults oviposited in phloem with lower stilbene glucoside contents. Phloem moisture differed at sites around the wound compared with that at a control site away from the wound, and the nitrogen content of entire bark cores was higher above wounds than at control sites away from the wounds. Phloem moisture correlated with the nitrogen content of entire bark. Phloem terpene contents correlated with each other, as did the stilbene contents. Associations between the host exploitation pattern ofD. micans and the biochemistry of the host phloem are discussed in relation to preselection by adults of sites suitable for larval development.

Mass production and purification of Euproctis chrysorrhoea (L.) nuclear polyhedrosis virus.

The rearing of larval Euproctis chrysorrhoea (L.) on an artificial wheatgerm diet is described. The larvae grew well on the diet, but took over ten weeks to complete their development, reflecting their prolonged life-span in the field. Using these larvae it was possible to mass produce a nuclear polyhedrosis virus (NPV) isolated from this species, with a view towards its use as a biological insecticide. A mean of 5.86 x 10(9) semi-pure NPV polyhedral inclusion bodies/g virus-killed larva was produced. The purification method described (simple centrifugation) removed over 99% of contaminant urticaceous hairs. Further purification through a sucrose gradient removed more hairs, but also resulted in a loss of NPV of about 35%.

The influence of weed-cover on the mortality imposed on artificial prey by predatory ground beetles in cereal fields.

Pitfall trapping was carried out in a field of winter wheat in the Vale of York to determine the levels of abundance of adult carabid and staphylinid beetles, (which formed the bulk of the natural predator complex) in the field. A point quadrat survey was carried out at the same time to assess the vegetation cover round each trap. Predation pressure by the beetles in the field was monitored using fruit fly (Drosophila) pupae as artificial prey. These artificial prey were attached to small cards inserted in the field adjacent to the pitfall traps.The numbers of beetles caught were found to be directly related to the frequency and density of Poa annua L. (annual meadow grass) the only abundant non-crop plant present at the time. More beetles were caught in areas where Poa was abundant than where Poa was scarce. This was probably related to the more suitable environmental factors offered by these of the wheat itself was found to be unrelated to captures.The number of fruit fly pupae taken was shown to be related to the numbers of carabid and staphylinid beetles present, and also to the type of vegetation occuring around each card.The implication of these results for the effects of predation on potential pest-outbreaks in the crop are discussed.