Action: Exclude introduced European earwigs from nest sites
Key messagesRead our guidance on Key messages before continuing
In California, USA, a replicated controlled trial showed that numbers of introduced European earwigs Forficula auricularia resting in solitary bee nest boxes can be reduced using a sticky barrier Tanglefoot. This treatment increased the use of the boxes by native bees.
Supporting evidence from individual studies
Thirty drilled pine wood solitary bee nest boxes were suspended from 15 valley oak trees Quercus lobata on the Cosumnes River Preserve, near Sacramento, Caifornia, USA, in 1990 (Barthell et al. 1998). The boxes each had twelve 10 cm-deep holes, 0.65 cm in diameter. Boxes were placed in pairs. One on each tree excluded crawling earwigs Forficula auricularia using the sticky barrier Tanglefoot. The treatment substantially reduced the number of earwigs found in the boxes and allowed a greater total number of bee cells (during the peak bee nesting week, there were 134 cells in boxes with Tanglefoot, 45 cells in untreated boxes). The majority of nesting bees in this study were native species of the leafcutter bee genera Megachile and Osmia although introduced species of Megachile were also present.