Comparison of fluorescent lights with differing spectral properties on catches of adult aquatic and terrestrial insects

Abstract

ABSTRACT The effectiveness of four different fluorescent light sources, used to attract adult aquatic insects (Ephemeroptera, Plecoptera, Trichoptera) and co-occurring terrestrial insects (Lepidoptera, Coleoptera, Diptera), was investigated. Blacklight (BL), blacklight-blue (BLB), cold white light (CW) and a blacklight/cold white light (BL/CW) combination were compared in a field trial with a fully-crossed factorial design. Each light treatment was also assessed at two levels of power (intensity): 16 W and 32 W. All light treatments attracted insects belonging to the six orders, but on average BLB and BL caught nearly 3 times more aquatic insects than CW, and about 1.5 times more terrestrial insects. The combination lights generally attracted intermediate catch numbers. Overall, BLB was most effective for attracting Ephemeroptera and Trichoptera, whereas BL attracted the most terrestrial insects, particularly Lepidoptera. Doubling the number of lights generally resulted in larger catches, but not significantly so (P > 0.05). We recommend that BLB lights be used in studies of adult aquatic insects because they are as effective as regular BL and appear to reduce the likelihood of attracting non-target terrestrial species; a favourable outcome with regard to faunal conservation and, more practically, sample sorting. Our results suggest that, for studies in remote locations, 16 W of light should be sufficient to obtain reasonable catches and, importantly, reduce the need to carry additional equipment, including heavy batteries.