Habitat fragmentation, the division of a continuous landscape into several smaller , more isolated areas, may result in nested distributions of species among sites, where the fauna of depauperate areas is a subset of that of species-rich areas. Twenty-one fragments of heath and woodland in the Sydney region were sampled using pitfall and water traps to collect ants, beetles, spiders, flies and wasps over six days in Autumn 1997. Monte Carlo simulations were used to examine the nestedness of assemblages of arthropod species in heath and woodland fragments in the Sydney region. Only flies in heath were significantly nested, while wasps in heath were significantly inversely nested; no other taxon in heath or woodland was significantly more nested than a random rearrangement of species among sites. The lack of nestedness found for arthropods may be due to characteristics related to their small size, high rates of endemism, dispersal and persistence, which operate independently and differently from vertebrates at the scale at which habitat fragmentation has been studied and nesting has been reported. This suggests that smaller fragments may support fundamentally different assemblages compared with larger habitat fragments, thereby limiting their value as reserves.