Arthropod diversity and abundance along the Kihansi Gorge (Kihansi River) in the Southern Udzungwa Mountains, Tanzania

Arthropod diversity and abundance at the order level was investigated along the Kihansi Gorge in the southern Udzungwa Mountains between June and August 1997 by using sweep netting, timed Lepidoptera counts, malaise-traps, solar powered light-¬traps, baited pitfall-traps, sticky-traps and baited butterfly traps. The study was undertaken to predict the possible effects of damming the Kihansi River above the fierce waterfall in the gorge. The gorge was divided into four micro-habitats, two of which are affected by waterfall spray (open spray, forest spray), and two of which were not affected directly by the waterfall (forest and riverine sites). The highest arthropod diversity was found in the forest spray, whereas the open spray contained the least. The forest spray area harboured the rarest arthropod orders. Arthropods are most abundant in the riverine site where 31 % of all sampled arthropods were recorded. The forest spray channel, forest site and open spray channel follow with 28 %, 23 % and 18 % of the sample respectively. It is suggested that the Mhalala Stream should be diverted to the gorge to replace the dammed Kihansi River. This would maintain at least partially the extraordinary micro-climate of the gorge and possibly retain the specialised arthropod community. Journal of East African Natural History Vol. 87 (1&2) 1998: pp. 233-24