Build an Insect Hotel: Boost Biodiversity and Shelter for Garden Insects

Insect hotels have received increased attention over the last few years, with the general public becoming more aware of insects' disappearance globally.

The numbers do not lie; 40% of the insect species are in decline, with an additional third endangered. The loss of insect abundance (populations) and diversity has detrimental effects on the whole ecosystem. For example, the lesser Kestrel, which has 40% of its breeding population, has been decreasing by 6% per year since 2012. The main driver of this stark decline is the reduced availability of large grasshoppers and crickets, vital for lesser Kestrel nestlings. This shows the effects of the loss of the insect population, which has been linked to land use change and the intensification of agriculture, which uses pesticides. One way to counter the decrease in insect species is by restricting pesticide use, prioritizing organic product consumption, and planting more flowering species in otherwise barren places. Another way to facilitate shelter for a wide variety of species is placing an insect hotel in a garden.

What is an insect hotel?

An insect hotel is a construction that facilitates the shelter and resting places for various insect species. The houses are often sold as a way for consumers to increase the insect diversity in their gardens. However, only placing the hotel is not sufficient to help the insects; the surroundings of the hotel should also cater to their needs; otherwise, they will not be able to populate it.

Layers of an Insect Hotel

Not all insects need the same materials and surroundings for their shelter or hibernation spots. Firstly, there is a distinction between flying insects and non-flying insects. For the flying insects, their shelters need to be placed higher off the ground to create safety. On the other hand, most of the more robust non-flying insects, for example, beetle species, need easily reachable areas close to the ground. To satisfy these preferences, the insect's layers are often placed in a certain way. These layers are often lacking in mass-produced insect hotels, which are often shaped like houses with different compartments. Examples of the layer and the species associated with it are wooden logs with several holes for solitary bees, pine cones for ladybugs, stones with wood chips for beetles, and the straw and clippings provide an overall habitat for generalist insects.

How to make an insect hotel

As mentioned before, there are different layers to an insect hotel, and it would be possible to pick and mix them. Most often, the focus is on bee species, which pollinate many flower plants. However, insects such as flies, wasps, and butterflies are often overlooked. Therefore, caring for a specific species or even a specific breed of species can be beneficial. By favoring endemic species over invasive species, the insect hotel can even be used for biodiversity conservation. However, it is good to do proper research on this since having the wrong diameters or materials that are preferred by invasive species can do more harm than good for the ecosystem. Luckily, there is a significant amount of information available on the preferred diameters of holes for (solitary) bee species or for wood-drilling insects; it mostly ranges between 2-13 mm, as can be seen in the picture below. The holes' depth changes with the holes' diameter; bigger diameters require deeper holes. Holes up to 6 mm diameter should be 5-12 cm deep, and holes bigger than 6mm should be 12-15 cm deep. These depths should be taken into account when drilling the wooden logs. Next, this article will show methods to create your own insect hotel and what materials are needed. Since the aim of this article is to increase knowledge on insect hotel purposes and promote the spread of insect hotels, the article is meant to be easily accessible and reproducible at a low to no cost. Based on materials that are often seen as waste products or as plentiful.

Things to consider before building the Insect Hotel

First, finding a suitable spot for your insect hotel is vital. Ideally, the insect hotel is in the sun the whole time to prevent moisture build-up and to create a warm habitat for the insects. Next, it should be in an area rarely disturbed by humans to create a tranquil environment. It is an additional bonus to place the insect hotel near areas with many flowering plants and/or near a water source; this is, however, not a must.

Materials you will need to build it:

To start the basis of the structure, either use wooden pallets (which can often be found at hardware stores for free) and either cinderblocks or bricks that have holes in them (solid bricks can also be used as a support). Next, the fillings of the different layers are needed; these can be a variety of materials, such as rocks, branches, green cuttings, dried cuttings, bark, and wood scraps. All of these do not have to be uniform in size; actually, the more diverse, the better. This diversity will create more niches inside the layers, and different insects can thrive in these niches.

For my insect hotel, I used the following materials:

2 wooden pallets
Olive cutting (1-2 days old)
4 untreated wood logs (more on specifics in methods)
2 cinder blocks
3 long hollowed-out bricks
4 long Bamboo sticks cut into pieces of various sizes
Wood chips
Straw or dried grasses
Various rocks of different sizes
Some pine cones

Equipment:

Electric drill
Drill bits ranging from 2 – 13mm
Saw
Chisel and hammer

Methods

First, prepare the wood logs, as explained in the picture below.

Next, cut the wooden pallets into several pieces, as shown below.

Time to stack the insect hotel with the different layers

First layer: stones and wood chips
Second layer: olive cuttings
Third layer: straw and bamboo (with some sand)
Fourth layer: cinder block in the center with pine cones surrounded by the four drilled wood logs
Fifth layer: upside down pallet with olive cuttings again

Finished product

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