Insect Hotels: A Refuge or a Fad?

If you are a gardener by hobby and a nature enthusiast by heart, chances are that you are already familiar with the concept of insect hotels (also known as bee hotels). Offering a sanctuary to beneficial insects, especially pollinators, insect hotels are considered to be the urban solution to declining population of beneficial insects in human environments due to habitat loss, pollution and abuse of pesticides. Insects provide many benefits to the ecosystem through pollination, nutrient cycle, and also as food source for birds.

Countless gardening stores and home furnishing stores sell insect hotels. Numerous blogs and websites have step-by-step manuals on how to build one yourself. All units are aesthetically pleasing which motivates well-intentioned buyers into adopting the concept. However, these insect hotels are often badly designed and they offer unsuitable home to the target insects. The warning sign of such designs is the unnecessary use of pine cones, glued snail shells, wood shavings and clear plastic tubes. Too many off-shelf insect hotels or build-your-own websites do not come with clear guide on maintenance, which is very important in ensuring the survival of the insects we intend to host.

Large insect hotels (aptly called insect condominiums) using wooden pallets are becoming very popular as individual or community gardening projects, sometimes to include non-insects such as frogs, toads and hedgehogs. In contrast, natural insect habitats occur as small separate nests, and large insect hotels pose risk of disease and parasitism to the insects inhabiting in high density inside. In fact, Rosita Moenen ^[1] observed that increasing number of badly-designed artificial nesting sites contributed to higher loss of (solitary) bees by parasitism.

Parasitism happens when kleptoparasites lay their eggs in tubes or cells occupied by bee larvae. Their larvae will hatch, consume the stored pollen and kill the bee larvae inside. Examples are parasitic wasps Melittobia acasta and Coelopencyrtus sp., and parasitic fly (Cacoxenus indigator) that attack red mason bees ^[1]. Insect hotels (especially large ones) make it very susceptible to parasitism. ^[1][2]. When not managed, the parasites will end up spreading to the rest of the insect hotels and will continue on for following seasons. In similar note, mould brings diseases to insects. It grows when moisture condenses and gets trapped in plastic materials ^[3] used in insect hotels as tubes and blocks. Lack of good roof/shelter on insect hotels, risking constant exposure to rain also contributes to mould growth.

The key solutions are correct designs, maintenance and nurturing environment.

While it seems on the surface that the insect hotels are more of a disadvantage and less of a sanctuary to the inhabitants, the concept is not a write-off. Everyone, from retailers to gardeners, is responsible to practise due diligence to ensure that these structures are designed and managed to minimise negative effects ^[2]. The key solutions are correct designs, maintenance and nurturing environment.

Here is the right approach to insect hotels:

1. Insect hotel or insect refuge? Start by thinking which type of insect you wish to host. For example, in the Netherlands, ^[4] only three types of bees are tube nesters, namely red mason bees (Osmia sp), leafcutter bees (Megachile sp) and bell bees (Chelostoma sp). These bees occupy only small tubes between 2 mm to 10 mm in diameter. For majority that are ground nesters such as bumblebees, mining bees, plasterer bees (also known as silk bees in Dutch) and many types of beneficial wasps, an insect refuge is a more effective approach instead.

2. Be realistic – small is better: Assess your area where you plan to set up your insect hotel or refuge. Think small and have multiple units housing one species rather than a single large one that attempts to host an entire zoo, requiring potentially conflicting environments. For example, hosting frogs and toads require humid environment with partial shade, while bee hotels need to be dry and in full sun. After you gain experience, you can build and create a different unit for another species.

 

3. Choose responsible design: There are a number of good guides online written by entomologists and wild bee experts. Marc Carlton ^[3] and Werner David ^[5] have written extensively on right designs for bee hotels, in English and German respectively. For non-bee hotels suitable for lady bugs, lace wings and non-migrating butterflies, Melanie von Orlow^[6] has written a book with detailed manuals, available in Dutch and German.

4. Build your own, build it right: Sourcing your own materials gives you peace of mind that your insect hotel is made of natural, untreated wood and without chemicals such as varnish, paint and wood protectant that will repel insects. To promote sustainability, consider using recycled or natural materials from your garden. If tubes are drilled into blocks, tubes should be smooth without splinters. Good insect hotels should be built sturdy with solid back and roof/shelter to protect from rain.

 

5. Install it well: For example, bee hotels ^[3] must be positioned in full sun, facing south east or south, at least a metre off the ground, with no vegetation in front of it obscuring the entrances to the tunnels. It must also be fixed securely to prevent shaking and swaying from wind.

 

6. Maintain and clean: This is the most overlooked part of having insect hotel. Taking care of insect hotel is just as important as building one. For example, bee hotels ^[3] should be inspected at the end of summer to remove and clean dead cells. This will prevent mould and mites that would multiply on the dead bees or larvae. Some experts recommend bringing occupied insect hotel into cool dry area such as garden shed during winter to protect the overwintering inhabitants from wind and rain.^[3] Without timely maintenance and clean-up, a once-occupied insect hotel may not attract a new batch next season.

 

7. Replace when it is time: Insect hotels can degrade naturally after two or more years because the material used is untreated. Change the nesting blocks or parts every two years to avoid build-up of mould, mites and parasites overtime.

 

Tips to make your garden an insect refuge:

1. Create sustainable nature: To encourage insects, especially pollinators, grow beneficial plants that that provide nectar and pollen. Choose native species ^[6][7] such as Lysimachia and Campanula flowers to promote natural biodiversity and avoid non-native plants.

2. An overly-manicured garden is not a refuge: Some non-migrating butterflies such as Papilio machaon overwinter as pupae attached to plants, so refrain over-trimming during autumn and spring ^[6]. Look out for ground nests of mining bees, bumblebees and beneficial wasps (German wasps and common wasps) before mowing or mulching your garden. It is easier to protect existing ground nests than to artificially create one.

3. Limit or no use of pesticides: Using pesticides (such as insecticides, fungicides and herbicides) will be counter-effective as it not only repels away or kill beneficial insects already living in your garden, it also disrupts the natural balance of a local ecosystem. Practise good housekeeping and maintenance so that you will never need to rely on pesticides in the first place. If such need arises, seek environment-friendly remedies or consult professionals instead.

 

Creating space for insects can be a very rewarding experience and it will teach you, your family and your community about natural diversity and sustainability. Make sure your next project becomes a refuge and not a fad. Your little friends and Mother Nature will thank you for it.

 

© Jo-Lynn Teh-Weisenburger, Entomologist

 

Jo-Lynn Teh-Weisenburger is an entomologist based in the Hague, the Netherlands. While her specialisation is on tropical insects that affect public health and agriculture, Jo-Lynn’s passion is to help people understand insects. When she is not scrutinising European insects and books about European insects, Jo-Lynn enjoys exploring recipes, yoga moves and foreign cities. Find her on LinkedIn: www.linkedin.com/in/jolynnteh

 

Acknowledgement:

Special thanks to Marc Carlton (http://www.foxleas.com) for his generous insight on this subject. His wealth of knowledge and experience on wild bees in UK and West Europe gave an impetus to many of references listed below.

(This article also made a guest appearance in WWF Amsterdam & The Hague Expat Team blog.)

References:

1. Moenen, R. (2012). De broedparasiet Cacoxenus indagator (Drosophilidae) en de parasitoïden Melittobia acasta (Eulophidae) en Coelopencyrtus sp. (Encyrtidae) bij solitaire bijen in kunstmatige nestgelegenheid. Entomologische Berichten, 1-2, 63-70. Retrieved September 8, 2017, from https://www.nev.nl/pages/publicaties/eb/nummers/2012/72-1-2/63-70.pdf.
2. Macivor, J. S., & Packer, L. (2015). ‘Bee Hotels’ as Tools for Native Pollinator Conservation: A Premature Verdict? Plos One, 10(3). doi:10.1371/journal.pone.0122126
3. Carlton, M. (2015, November 13). How to Make and Manage a Bee Hotel: Instructions that Really Work. Retrieved September 07, 2017, from http://www.foxleas.com/make-a-bee-hotel.asp
4. Koel, H. (n.d.). Dutch Bees and their relations – Survey of solitary and social living bees (Apidea s.l.) in The Netherlands and Flanders. Retrieved September 07, 2017, from http://www.wildebijen.nl/beeguide.html
5. David, W. (n.d.). Schautafeln Nisthilfen (Insektenhotels) u. Wildbienen. Retrieved September 13, 2017, from https://www.naturgartenfreude.de/wildbienen/nisthilfen/schautafeln/
6. Von Orlow, M. (2014). Bouw Je Eigen Insecten Hotel: 30 Eenvoudig Zelf Te Bouwen Nestkasten (G. Meesters, Trans.). Utrecht: Kosmos Uitgevers.
7. Koel, B. H. (n.d.). Insectenplanten, wilde bijen en hun relaties – Overzicht van waardevolle planten voor solitaire en sociale bijen (Apidea s.l.). Retrieved September 08, 2017, from http://www.wildebijen.nl/insectenplanten.html

Images sources:

1. Bee hotel comparison by David Werner (https://www.naturgartenfreude.de/wildbienen/nisthilfen/schautafeln)
2. Red mason bee (Osmia rufa), photo by Saxifraga – Pieter van Breugel (http://freenatureimages.eu)
3. Large leafcutter bee (Megachile willughbiella), photo by Saxifraga – Pieter van Breugel (http://freenatureimages.eu)
4. Bell bee (Chelostoma rapunculi), photo by Saxifraga – Pieter van Breugel (http://freenatureimages.eu)
5. Recommended bee hotel design by David Werner (https://www.naturgartenfreude.de/wildbienen/nisthilfen/schautafeln)
6. Yellow loosestrife (Lysimachia vulgaris), photo by Saxifraga – Willem van Kruijsbergen (http://freenatureimages.eu)
7. Rapunzel bells (Campanula rapunculus), photo by Saxifraga – Bart Vastenhouw (http://freenatureimages.eu)
8. Common carder bee (Bombus pascuorum), photo by Saxifraga – Peter Meininger (http://freenatureimages.eu)