Soil arthropod biodiversity is an indicator of soil quality and can be studied using pitfall trapping. In this research, olive grove
edaphic fauna was assessed at different sampling dates by comparing two different diameters (7 and 9 cm) and three different contents
(empty, water and preservative) of pitfall traps in order to determine which type of pitfall trap is more efficient. Considering all
pitfall trap types and sampling times, a total of 12,937 individual edaphic arthropods belonging to 11 taxa were recovered. Smaller
traps with preservative collected significantly more individuals than the other pitfalls tested. Larger and empty traps collected significantly
more spiders and traps with preservative collected more beetles. Smaller and empty traps collected fewer individuals than
the other trap types. Both Shannon’s diversity and Pielou’s evenness indexes were higher in the larger and empty traps and richness
was higher in the smaller traps filled with water. The study of myrmecocenosis was emphasised because olive grove soil fauna was
numerically dominated by Formicidae (56.6% of all organisms captured) belonging to 12 genera and 24 species; Tapinoma nigerrimum,
Messor barbarus, Cataglyphis hispanicus, Tetramorium semilaeve, Cataglyphis ibericus, Messor bouvieri and Camponotus
cruentatus were the most abundant ant species. Traps with preservative reached the highest accumulation of species for a small
number of pitfalls when compared with the other pitfalls studied and a sampling effort of 20 samples is apparently sufficient to
sample the greater part of the ant species of the olive grove. From this study, it seems that traps with preservative are the best choice
to use in further studies concerning the epiedaphic fauna of the olive grove.
