Monitoring Exotic Beetles with Inexpensive Attractants: A Case Study

SIMPLE SUMMARY: Detecting and monitoring exotic and invasive beetles is a complex activity, and multiple species still manage to evade controls. Citizen science can be an important adjunct in alien species monitoring programs, but to have a greater chance of success, it must employ traps and attractants that are easy to gather and use. Bottle traps baited with food products are successfully used during long term faunistic surveys, and the same methodology can be adapted to alien species detection and monitoring. In this article, we tested the use of bottles baited with apple cider vinegar, red wine, and 80% ethyl alcohol in capturing exotic and invasive beetles in the surroundings of Malpensa Airport (Italy). The traps proved effective, and in the traps with vinegar as an attractant, they captured four out of five invasive Nitidulidae, as well as the only invasive Scarabaeidae present in the area. Popillia japonica’s response to apple cider vinegar is documented for the first time and suggests the use of this attractant in monitoring surveys for this species, especially if supported by citizen science programs. The substantial reduction in the activity time of the traps seems to have considerably reduced collateral catches of native fauna. ABSTRACT: Detecting and monitoring exotic and invasive Coleoptera is a complex activity to implement, and citizen science projects can provide significant contributions to such plans. Bottle traps are successfully used in wildlife surveys and can also be adapted for monitoring alien species; however, a sustainable, large scale trapping plan must take into account the collateral catches of native species and thus minimize its impact on local fauna. In the present paper, we tested the use of bottles baited with standard food products that can be purchased in every supermarket and immediately used (apple cider vinegar, red wine, and 80% ethyl alcohol) in capturing exotic and invasive beetles in the area surrounding Malpensa Airport (Italy). In particular, we reduced the exposition type of the traps in each sampling round to three days in order to minimize native species collecting. We found a significant effect of the environmental covariates (trap placement, temperature, humidity, and forest type) in affecting the efficiency in catching target beetles. Nearly all invasive Nitidulidae and Scarabaeidae known to be present in the area were captured in the traps, with apple cider vinegar usually being the most effective attractant, especially for the invasive Popillia japonica.