A NOVEL AERIAL-INTERCEPTION TRAP FOR ARTHROPOD SAMPLING

Abstract

Although there are many field techniques to estimate the abundance and diversity of arthropods in terrestrial ecosystems, all have significant limitations (Chapman and Kinghorn 1955, Southwood 1978, Masner and Goulet 1981, Canaday 1987, Atkinson et al. 1988, Chenier and Philogene 1989, McEwen 1997, Dobony and Edwards 2001). In particular, methods for sampling arthropods moving through the air usually have major drawbacks, such as high cost per unit or difficulty of installation and sample retrieval. When I wished to assess the affect of fire on the arthropod community in Florida scrub at the Archbold Biological Station in Highlands Co., I also was faced with the problems of replicate sampling at several different locations and dealing with severe thunderstorms accompanied by high wind and torrential rainfall. Here I describe a novel trap that solves some of the aforementioned problems. The trap consisted of an array of four transparent, recycled 2-liter polycarbonate beverage bottles, each having a 17 cm wide x 13 cm high strip in its side removed to allow the entry of arthropods. When viewed from the side, the area of the opening in each bottle was 10.5 x 13 cm. Hence, the effective surface area of the trap with four bottles was 550 cm2. The intact bottom of each bottle served as a reservoir for -200 ml of collecting fluid, such as soapy water. The bottles were suspended by their caps that were bolted in a 2 x 2 array centered on the underside of a 20 x 30 cm piece of 1.3 cm (0.5 in) thick exterior grade plywood (Fig. 1). This conformation stabilized the bottles in windy conditions. The wooden platform provided, along with the top portion of the bottles, shelter from precipitation. Each trap was mounted on two 1.3 cm (0.5 in) diameter x 2.5 m steel reinforcing rods (commonly called rebar) placed vertically to a depth of 30-40 cm in the soil. After the tops of the rods were slipped through the two 1.6 cm (5/8 in) holes near the ends of a platform (Fig. 1), the trap was lowered to the desired position 0.5, 1.0, or 1.5 m above ground and held in place by medium binder clips attached to the rods beneath the platform. For additional stability in high winds, a second binder clip could be attached to a rod just above the plywood platform. The cost of each trap, including the two rods, was $1-2. Furthermore, I found that I could assemble and install a dozen traps at 10 m intervals along a transect in the scrub in 2-3 h. Arthropods were removed from the four reservoirs in each trap by aspirating the fluid with a I 30cm