Suction duration and numbers of Araneae and Auchenorrhyncha collected in grassland when using an open-ended cylinder to define the sample area

Suction samplers are typically used with touch-down samples, where the nozzle is held stationary on the ground, or within an open-ended cylinder, where the nozzle is moved through the enclosed vegetation. With touch-down sampling, published estimates suggest that virtually all individuals and species of grassland invertebrate are captured within 3 s. Effects of suction duration on catch when sampling within a cylinder have rarely been investigated. Here, it was found that extrapolation from studies of touch-down sampling, based on the relative areas of the G-vac nozzle and the cylinder, can be used to guide minimum sampling durations for Auchenorrhyncha (leafhoppers and planthoppers) when using a G-vac. Additional time, however, may be necessary when sampling Araneae (spiders), probably because movement of the G-vac nozzle within the cylinder results in disturbance of the vegetation such that more specimens are made available to be captured than with touch-down sampling

Suction samplers for grassland invertebrates: the species diversity and composition of spider and Auchenorrhyncha assemblages collected with VortisTM and G-vac devices

The species composition of samples of spiders and Auchenorrhyncha obtained using a Vortis™ and a modified garden leaf-blower / vacuum „G vac‟ was compared at three sites using standard sample areas and suction times. Both devices caught scarce method-unique‟ species not found by the other, but the G-vac caught more. The G-vac also caught a larger number of specimens in total. Rarefaction and extrapolation were therefore used to quantify three measures of species diversity (Hill numbers) with standardised sample size and sample coverage. Traditional rarefaction and extrapolation curves for the two devices, based on sample size, were not significantly different, however, estimates of species richness were higher for the G-vac than the Vortis at some levels of sample coverage implying a higher efficiency at discovering additional species using the G-vac. Some individual species were more abundant in the G-vac samples, but they were not associated with a specific microhabitat. There was, therefore, no evidence that the two devices were sampling different communities. The study reveals that Vortis and G-vac devices can provide consistent inventories of the more abundant species of spiders and Auchenorrhyncha, but that more scarce species are found with the G-vac, and fewer samples may be required with this device because of its tendency to capture more specimens per sample