Insect Conservation and Diversity (2015) 8, 189–192 doi: 10.1111/icad.12095
SHORT COMMUNICATION An artificial nesting substrate for Osmia species that nest under stones, with focus on Osmia inermis (Hymenoptera: Megachilidae)
CORY S. SHEFFIELD,1 MARGIE A. WILKES,2 G. CHRISTOPHER 3 2 CUTLER and LUISE HERMANUTZ 1Invertebrate Zoology, Royal Saskatchewan Museum, Regina, Saskatchewan, Canada, 2Department of Biology, Memorial University, St John’s, Newfoundland, Canada and 3Department of Environmental Sciences, Dalhousie University, Truro, Nova Scotia, Canada
Abstract. 1. Several megachilid bees are excellent crop pollinators, and many species show potential for management as they nest in pre-existing cavities in artificial substrates. Some species, particularly in the Osmiini, however, have nesting habits not conducive to conventional trap-nesting. Here we report on an artificial nest for species of Osmia bees which normally build nests on the underside of stones. 2. The Holarctic species Osmia inermis accepted overturned terracotta saucers as nesting sites, with 10% of the saucers occupied in the fall of 2011. 3. These saucers are inexpensive and available in many sizes, facilitating fur- ther scientific study of this, and other species. Implications of using artificial nests for managing this bee for crop pollination, and for its conservation, are discussed. Key words. artificial nest, pollination, pollinator conservation, rare species.
Introduction & Kemp, 2002). With at least 346 species globally (Ascher & Pickering, 2014), almost 25% of which are confirmed Many species in the bee family Megachilidae (Hymenop- nesters in wood and/or stems with preexisting cavities tera) show good potential as managed crop pollinators (tallied from Cane et al., 2007; Rightmyer et al., 2013; and may benefit highly stressed agricultural systems that Muller,€ 2014), the potential for success is great. typically rely on one managed pollinator, the European Of the megachilid bees, tribe Osmiini shows the greatest honey bee (Apis mellifera L.) (Apidae). Many megachilid diversity in nesting habits (Muller,€ 2014). This is particu- bees nest naturally in preexisting cavities (Michener, larly true within genus Osmia, as many species do not 2007), and many will accept a range of artificial nesting readily accept traditional trap-nests due to different and/or substrates collectively called ‘trap-nests’ (Krombein, 1967). more specific nesting preferences. There are several Osmia There is a long history of using trap-nests to observe the species that excavate nests into the soil [e.g. the odontogas- natural history of bees, and artificial trap-nests can serve ter species group of the subgenus Melanosmia; see Rightm- as nesting sites for bees in a range of habitats (Sheffield yer et al. (2013) and Muller€ (2014)] or pliable materials et al., 2008), thus facilitating the conservation and encour- (Cane, 2012), and masons which build nests on the sides agement of native pollinator species in natural and and/or undersurface of stones, or in more specialised sub- anthropogenic landscapes. Detailed trap-nesting studies strates such as snail shells (Rau, 1937). Cane et al. (2007) have been crucial to optimise the use of non-Apis bees in and Rightmyer et al. (2013) provide recent summaries of crop pollination, and with growing concern over declining nesting for North American species of Osmia, and Muller€ availability of commercial pollinators, there is interest in (2014) provides a detailed summary of Palearctic species. further developing Osmia bees for crop pollination (Bosch Some Osmia species with specialised nesting habits may be as prolific as wood/stem nesting species. Richards et al. (2011) reported Osmia (Diceratosmia) conjuncta (Cresson), Correspondence: Cory S. Sheffield, Royal Saskatchewan a snail shell nesting species of eastern North America Museum, Invertebrate Zoology, 2340 Albert Street, Regina, Sas- (Rau, 1937; Cane et al., 2007), as one of the most katchewan, Canada S4P 2V7. E-mail: Cory.Sheffi[email protected] abundant bee species in Carolinian habitats in southern
Ó 2014 The Royal Entomological Society 189 190 Cory S. Sheffield et al.
Ontario, Canada, accounting for almost 10% of total bees glazed), are relatively inexpensive (i.e. $2–3 CND, versus captured in that study. Osmia (Melanosmia) tarsata Pro- ca $20 for a typical commercially available solitary bee vancher, a soil nesting species, is common in some low- nesting box), are available in a range of standardised bush blueberry fields in Quebec, Canada (C. S. Sheffield, sizes, will break down naturally and are easy to install in pers. obs.), and is considered an important pollinator of the field. Nesting saucers were placed in commercially this crop in Maine (Rust and Osgood (1993), as species managed lowbush blueberry (Vaccinium angustifolium O. kenoyeri (Cockerell). Hicks (2009) found a large nest- Aiton) (Ericaceae) fields and unmanaged lowbush blue- ing aggregation of almost 170 O. (Melanosmia) inermis berry patches in Grand-Falls Windsor (49°00036.1″N, (Zetterstedt) cocoons under metal debris in a lowbush 55°38031.1″W) and Colliers (47°26032.0″N, 53°18059.8″W), blueberry field in eastern Newfoundland, Canada. This Newfoundland and Labrador, Canada, on May 5, 2011 suggests that it would be possible to facilitate population and collected on August 30, 2011. Nesting saucers were growth of Osmia with alternative nesting habits, which used in two sizes: 15.5 cm diameter 9 2.4 cm deep, and could have ramifications for bee conservation and crop 23.5 cm diameter 9 3.0 cm deep. At each study site, nest- pollination in a range of habitats. ing saucers were placed within fields where there were Here, we report on a simple method of increasing popu- patches of bare ground or areas that were relatively free lations of surface nesting Osmia using an artificial, stan- of vegetation (Fig. 1b); any plants that were present were dardised nesting substrate (i.e. overturned terracotta removed so that no vegetation would grow to impact the saucers), henceforth referred to as ‘nesting saucers’. nesting saucers. The ground was patted down by hand, and each nesting saucer was rotated while being pushed downwards to seal the edge into the soil. A 2–3 cm wide Material and methods entrance tunnel was created under the lip of each nesting saucer (Fig. 1a). Sixty nesting saucers were placed in the Nesting saucers (Fig. 1a) were used as surrogates for field in 15 groups of four (Fig. 1b), with each group hav- stone nesting substrates as they provide a similar level of ing both large and small diameter saucers. In the fall, the protection from weather (especially if the upper side is nesting saucers were sealed with aluminium foil-coated
(a) (b)
(c) (d)
Fig. 1. Nesting saucers used as an artificial nesting substrate for osmiini bees, showing (a) placement of an individual nest on the ground, with a small opening; (b) nest grouping, showing two different sized nests; (c) small and (d) large nesting clusters of Osmia inermis.
Ó 2014 The Royal Entomological Society, Insect Conservation and Diversity, 8, 189–192 Artificial nest for Osmia bees 191 sheets of cardboard and overwintered in an outdoor shed. (Bosch, 2008; Zurbuchen et al., 2010). Simple and Bees were collected and preserved after emergence. economical nesting materials, such as those investigated here, provide the opportunity to ‘trap’ bees one season, and relocate the nests to areas of the field where pollina- Results and discussion tion/pollinators might be lacking. With a way to manage O. inermis, and potentially other Osmia species sharing Osmia inermis is a Holarctic species found in boreo-alpine this nesting habit, it might be possible to add additional zones, and at low altitudes north of the Arctic Circle species to the list of managed pollinators of crops. (Rightmyer et al., 2010). This species typically builds nests Although scarcity of nesting habitat is not likely a con- under stones (Priesner, 1981; Else & Edwards, 1996) in tributing factor for the rarity of O. inermis in its natural sites with short vegetation. Of the 60 nesting saucers habitat in the UK, providing additional artificial nesting deployed, six (10%) were used by O. inermis females as sites may be a viable way to increase the abundance of nesting sites, four in Grand-Falls Windsor, two in Col- this species and/or relocate populations to other sites, liers. No preference for nesting saucers size was observed, assisting in its conservation. as three of both sizes were used. Nests ranged in size from clusters of three (Fig. 1c) to over 15 cells (Fig. 1d), though clusters of over 150 cells have been reported under Acknowledgements larger structures (Hicks, 2009) as several females may use the same nesting site (Priesner, 1981; Else & Edwards, We thank the property owners in Grand-Falls Windsor 1996). Parsivoltinism, where one generation develops and and Colliers for access to field sites used in this study. emerges over at least a two-year period, has also been This represents publication 127 of the Natural Sciences reported for this species (Smith, 1851), which may help and Engineering Research Council Canadian Pollination explain the large nesting aggregations (e.g. Hicks, 2009). Initiative (NSERC CANPOLIN), who provided the Cohort-splitting is probably important for this cold- funding. adapted species, as many areas throughout its range expe- rience prolonged, inclement early summer weather (BWARS, 2014). This is supported in this study, as only References 34 adults were reared from 51 nesting cells, though un- emerged cells were not dissected to determine mortality. Ascher, J.S. & Pickering, J. (2014) Discover Life Bee Species Guide Osmia inermis is considered polylectic (see Muller,€ and World Checklist (Hymenoptera: Apoidea: Anthophila). 2014). In North America, O. inermis has often been asso-
Ó 2014 The Royal Entomological Society, Insect Conservation and Diversity, 8, 189–192 192 Cory S. Sheffield et al.
Macdonald, M., Bland, K., Edwards, M. & Little, B. (2008) Visit genera, synonymies and nesting biology revisited. Systematic to Blair Atholl Area to Assess Known and Potential Osmia iner- Entomology, 38, 561–576. mis Sites. Hymettus, West Sussex, UK. Rust, R.W. & Osgood, E.A. (1993) Identification of Osmia Michener, C.D. (2007) The Bees of the World, 2nd Edition. Johns kenoyeri and O. virga (Hymenoptera: Megachilidae), two blue- Hopkins University Press, Baltimore, Maryland. berry pollinators. Entomological News, 10, 113–117. Muller,€ A. (2014) Palaearctic Osmiine Bees, ETH Zurich€ Sheffield, C.S., Kevan, P.G., Westby, S.M. & Smith, R.F. (2008)
Ó 2014 The Royal Entomological Society, Insect Conservation and Diversity, 8, 189–192