Invader effects in a community of cavity nesting Megachilid bees (Hymenoptera: Megachildae)

Published source details Barthell J.F., Gordon W.F. & Thorp R.W. (1998) Invader effects in a community of cavity nesting Megachilid bees (Hymenoptera: Megachildae). Environmental Entomology, 27, 240-247.
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This study is summarised as evidence for the following.

	Action	Category
	Exclude introduced European earwigs from nest sites Action Link
	Provide artificial nest sites for solitary bees Action Link

Exclude introduced European earwigs from nest sites

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.
Provide artificial nest sites for solitary bees

Thirty to 45 drilled pine wood solitary bee nest boxes were suspended from valley oak Quercus lobata trees on the Cosumnes River Preserve, California, USA in 1989 and 1990 (Barthell et al. 1998). The boxes each had twelve 10 cm deep holes, 0.5, 0.65 or 0.8 cm in diameter. In both years, the European earwig Forficula auricularia was the most common occupant (59-85% of all occupied nests), followed by two introduced leafcutter bee species Megachile rotundata and M. apicalis (19.6% of all occupied nests in 1989, 3.4% in 1990). Four native bee species also occupied the boxes, but in much lower numbers. Megachile angelarum was found in 3.2-3.8% of occupied nests. M. fidelis, M. gentilis and Osmia texana occupied less than 1% of occupied nest boxes in both years.