I making a bug hotel, but I don't know what diameter I need to make the holes. I'd like to attract as many different types of insect.
Different sizes for different insects. Use dry hollow stems such as bamboo canes tied in bundles and stuffed in some old pipe or a bird's nest box with the front taken off. If drilling in a block of wood use a 6, 8 and 10 bit for diffrent size holes.
I'm copying an idea I saw at the RHS stand at the Harrogate show. They rolled newspaper around pencils. But I'm wondering about using clear straws as well, as you could see what is inside them.
The photo shows a somewhat grandiose "Insecthotel" I spotted whilst on holiday in Austria last autumn. [Priced at 147 Euros, it was a tad outside my price range....].
However, it may serve as a model for those of us who prefer to make our own 'kit' - rather than pay outrageous prices, or excess baggage charges to Mr Ryan etc..!!
I've got to build something. I thought the bugs had plenty of scope to make their own in my garden. They do, but the finding and viewing isn't so good for me.