Do bug hotels actually work?

Some designs do and many do not — the elaborate multi-compartment structures sold in garden centres are largely decorative, while a few simple features genuinely support insects.

What works, and why:

Drilled holes for solitary bees. Holes of varied diameter, roughly 2 to 10 millimetres, drilled into solid untreated wood, at least 10 centimetres deep, smooth inside, closed at the back, facing south or south-east and sheltered from rain. Mason and leafcutter bees readily use these, and they are excellent pollinators.

Hollow stems — bamboo or cut reed — provided they are cut cleanly at a node so the back is sealed, and are not splintered.

Log piles and standing deadwood, which support beetle larvae over years.

Leaf litter left in place, and hollow plant stems left standing over winter, which is where a great many insects actually overwinter — the single most effective thing is tidying less.

What does not work, or actively harms:

Pine cones, straw, wood shavings and plastic tubes, which fill the large decorative compartments and support little. Plastic and glass tubes cause condensation and mould that kills larvae.

Structures left uncleaned for years, which accumulate parasitic mites and fungal disease. Occupied tubes should be replaceable, and a design that cannot be cleaned becomes a trap.

Rough or splintered holes, which damage bees' wings.

Very high densities in one place, which concentrates parasites — the opposite of how solitary bees naturally distribute.

Ladybird and lacewing compartments, which are rarely used as intended.

The honest framing. Nesting sites are usually not the limiting factor; food and pesticide exposure generally are. A bug hotel beside a sterile lawn achieves little, while flowering plants across a long season, no pesticides, some bare soil for ground-nesting bees — which are the majority — and undisturbed corners achieve a great deal.

Their real value may be educational, which is a legitimate reason to have one, stated honestly.