Design and evaluation of a novel and inexpensive floating emergence trap for aquatic insects in shallow water

Background/Question/Methods

Floating emergence traps can be an effective method of sampling the abundance, temporal patterns and diversity of adult insects emerging from an aquatic habitat. Emergence sampling has a wide range of applications in ecological research and the monitoring of pollution. An operative emergence trap for aquatic ecosystems must cause minimal shading and disturbance to the trapping area, exclude foreign adults from entering the trap, and withstand prolonged exposure to variable weather. The trap design presented was developed for an undergraduate research project on the prey availability of nesting tree swallows (Tachycineta bicolor) in naturally acidified ecosystems. The study began with a trial period to test the performance of the traps. This design allows for the construction of traps using only affordable and commercially available components that need minimal modification. It also possesses novel features, unseen in previously published designs, including its ability to be collapsed for portability and storability. The traps were placed in an artificial stream-fed pond (a former cranberry bog reservoir) in the New Jersey Pine Barrens. Collections were retrieved weekly and sorted to order, except for Diptera, which were sorted to the paraphyletic groups of Nematocera and Brachycera.

Results/Conclusions

Preliminary results from four weeks of trapping, from April to May of 2011, using five traps (1 m² each), yielded 2,708 adult insects, with a majority of Nematocera at 2,560. The remainder of the collections was represented by Brachycera and four other insect orders. This trap design, with the inclusion of other sampling methods, should prove to be a viable method of sampling prey availability for tree swallows throughout the nesting season. The trial period confirmed the trap’s ability to effectively sample aquatic insect emergence and produced satisfactory results in regards to the trap’s quality, practicality, and durability. The trap’s improvement upon the drawbacks of previous designs and its performance in the field indicate that this design is a simple and inexpensive alternative to previous floating emergence traps, and the novel features make it an attractive and replicable option for future emergence research in a variety of disciplines.