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Document Type

Peer-Review Article

Abstract

Because relatively few nymphs of Odonata are caught in most drift studies, they have been inconsistently reported and little is known about the species and life stages that are predisposed to drift. We used large drift nets with relatively coarse mesh sizes (1500 µm) to sample late-instar odonate nymphs in two large rivers in Wisconsin. These nets were presumed to have advantages over smaller, conventional aquatic insect drift nets, including the capability to sample greater water volumes more quickly, sampling for longer periods of time before nets become clogged with debris, and a reduced likelihood of large, active insects escaping from the nets. Nymphs of 14 species of Odonata in five families were caught, but drift densities were low (0.042 m-3 overall; -3 for most species) and final instar nymphs (F-0) were collected less frequently than younger nymphs (F-1 through FOphiogomphus comprised 78% of the total in the St. Croix River. Ophiogomphus howei Bromley was the most commonly sampled species (drift density of 0.026 m-3), with at least five instars collected.

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Entomology Commons

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