Spiders were sampled by knockdown insecticide fogging from the canopies of tropical rainforest sites in Dumoga-Bone National Park, Sulawesi, at altitudes of 210 m, 300 m, 400 m and 1150 m. The density of spiders in the canopies increased with altitude from 0.97 m−2 at 210 m to 14.6 at 1150 m−2. Species numbers increased five-fold between 210 m and 1150 m but species diversity (α of the log series) was greatest at 210 m and least at 1150 m, partially due to dominance of the fauna by few species at the highest altitude. Similarity between the spiders' communities (as measured by the Morisita-Horn index) was greatest between canopies at 300 m and 400 m and least at 400 m and 1150 m.
Theridiidae were abundant in forests at all altitudes, Pholcidae and Salticidae in the lowland forests between 210 m and 400 m and Clubionidae, Linyphiidae and Oonopidae in the montane forest at 1150 m. Theridiidae was the most species-rich family at all altitudes (22−30% of all species). Other species-rich families included Araneidae (7−19%) and Salticidae (8−17%) in lowland forests and Clubionidae (12%), Oonopidae (10%) and Salticidae (12%) in the montane forest.
Published information on density, proportion and diversity of spiders in canopies of both tropical and temperate trees is reviewed and the results discussed in relation to those from the present study.