We undertook a comparative study in 2004 at Writtle College, Chelmsford, Essex, UK, using box quadrat, open quadrat and transect sampling techniques, to ascertain the significance of emigration and immigration of individuals from survey plots during sampling and the implications for abundance estimation and subsequent calculation of assemblage diversity. Both open quadrat and transect techniques consistently produced underestimates of total Orthoptera density, Chorthippus nymph density and Chorthippus parallelus adult density, when compared to box quadrat sampling, although the differences between techniques were not statistically significant. We suggest that these underestimates of density using the former techniques were due to individuals escaping from the observer during sampling, whereas individuals jumped onto the high sides of the box quadrats.
Both open quadrat and transect monitoring tended to miss the tettigoniids Metrioptera roeselii and Conocephalus discolor, leading to underestimates of species richness when compared to box quadrat sampling. We suggest that if surveyors wish to ascertain bushcricket abundance or species richness at a study site, methods that constrain movement of individuals, such as box quadrats, should be used.