A pheromone-baited pitfall trap for monitoring Agriotes spp. click beetles (Coleoptera: Elateridae) and other soilsurface insects

Pheromone traps have been developed specifically for the survey, research and management of click beetles (Coleoptera: Elateridae) in temperate North America (NA), Europe and Asia (Ritter and Richter 2013; Vernon and van Herk 2013; Traugott et al. 2015). These include: ‘Estron Traps’ for survey of Agriotes species in the former USSR (Oleshchenko et al. 1987); ‘Yatlor Traps’ for survey and scientific study of Agriotes in Europe (Furlan et al. 2001), and; ‘Vernon Beetle Traps’ for survey and integrated pest management (IPM) of invasive Agriotes in NA, i.e., A. obscurus (AO), A. lineatus (AL) and A. sputator (AS; Vernon 2004). Although effective, these traps are no longer available commercially, although the Yatlor Trap has been re-designed as a funnel trap to better intercept various flying Agriotes in Europe (Csalomon, Budapest, Hungary). The loss of the Vernon Beetle Trap (VBT) and customized lures for AO, AL and AS [formerly produced by Contech Enterprises Inc., Delta, British Columbia (BC), Canada] necessitated the development of a new trap for use in Agriotes IPM program development in Canada. Based on the authors’ experience with earlier Agriotes traps, the new trap was designed to: provide trapping efficacy comparable to the VBT; reduce the time required for assembly, installation and inspection; exclude insectivorous vertebrates and water, and; be consistent, reliable, inexpensive, small, easy to transport, and durable. The new trap, named the Vernon Pitfall Trap® (VPT) (Fig. 1), is constructed of durable polypropylene, and is formed from three custom injection molds (Exact Molds Ltd, Abbotsford, BC). Two essential components are an in-ground pitfall chamber for specimen collection (Fig. 1A) and a protective cover containing a pheromone-bait holder and vertebrate-exclusion cage (Fig. 1B). The pitfall chamber forms a tapered cup that is 10 cm high from base to apex of the trap, with a 5.8-cm-diameter base (inside diameter, ID) and a 9-cm-diameter opening (ID) (Fig. 1A). The inside of the cup, three centimetres from the apex, is molded to receive a commercially available specimen cup (specifically, FisherbrandTM 4.5-oz. Polypropylene Graduated Specimen Container). These removable containers, which can be filled with a preserving liquid such as propylene glycol or used without, and accompanying lids are used for labelling and storing collected specimens. Surrounding the apex of the chamber is a rounded collar that slopes gradually away from the opening (3 cm outward and 1 cm downward), with a steeper decline 0.5 cm from the outermost edge. The collar has raised ridges (0.1 mm high) spaced 1–2 mm apart to enable climbing by walking insects (Fig. 1A and D). Beneath the collar are four evenly spaced supports that link the collar to the chamber to provide rigid stability to the trap. At the apex of the collar are two 1.2-cm-diameter (outside diameter, OD) x 2-cm-high hollow wells, spaced 8.5 cm apart, which receive and secure the trap lid (Fig. 1A and D). The shape of the pitfall chamber is similar to typical hand-held or upright bulb planters, which can be used to quickly remove exact soil cores for tight trap insertion. Moreover, overlapping traps can be conveniently stacked for transport. When the base is inserted into the cored soil, foot pressure on the reinforced collar seals the base tightly to the