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Flowers, Fruits, and Frass

Welcome Beneficial Guests with an Insect Hotel

Originally published by Kelly Allsup on June 21, 2016.

Did you know that with minimal investment, you can open a hotel? Insect hotels offer places for beneficial insects and pollinators to survive winter's chill and to nest in spring and summer. You can use them to employ garden warriors in any flower bed, vegetable garden, or fruit orchard.

Insect hotels can be all sizes, from a small box filled with materials to an elaborate structure ready for many residents. Most insect hotels are built out of recycled materials such as pallets, bricks, drain tiles, and old logs. You can mimic the forest floor with leaves, straw, mulch, cones, and sticks. Your hotel can be as simple or elaborate as your creativity leads.

Most are placed in shadier locations under trees, with a bee habitat located in the sunniest spot. Bamboo sticks and stems of sunflowers, Joe pye weed, or Sambucus can be used to shelter 30% of the solitary native bees. Some builders add protective bird netting, shutters, or roofs to prevent the hotels from becoming bird buffets.

Understanding how insects overwinter and the guests you will attract will help you engineer your hotel. Some insects, like Monarchs and Painted Ladies, flee to the south. Others endure the Illinois winter by going into a suspended state of development called diapause, employing proteins that act as an antifreeze to enable survival.

Who might you attract?

Hoverflies overwinter as pupae in leaf debris, pine cones, and straw. Green lacewings prefer to pupate in rolled-up corrugated paper. Both species are pollinators as adults, but their larvae are ferocious hunters of aphids. You need good sources of nectar and pollen for the adults to be attracted to the garden.

Ladybugs survive as adults under branches and in logs. Most adults sold in garden centers are harvested from the wild. However, upon release they rarely stay in the area you intended. Instead, you can entice them to stay in the garden by offering habitat and food. Ladybugs lay their eggs near aphid colonies.

Butterflies and moths overwinter in varying stages. Swallowtail butterflies and cecropia moths overwinter in the chrysalis (pupal) stage. Purplish coppers overwinter as eggs in debris, and Baltimore checkerspot caterpillars spend their winter in leaf litter. Few moths overwinter as caterpillars, but wooly bears can be suspended in snow and ice and wake up when temperatures warm. Be aware that cleaning up under and around butterfly plants in the fall can eliminate overwintering populations.

Spiders overwinter as adults; they may stay active even in really cold temperatures but seek out shelter to stay warm. They usually hibernate as immatures under loose bark or as egg cases.

Parasitic wasps can burrow into trees, so including wood blocks with holes may lure them to your insect hotel. Although most adults feed on nectar and pollen from flowers, they lay their eggs in the bodies of garden pests. Most notable is the parasitic wasp that lays its eggs in the tomato hornworm, where white pupae can be seen in great numbers.

All of a bumblebee colony dies out except for newly produced queens, which will burrow into a tree stump. An upturned flower pot filled with straw or garden debris can easily become the queen's winter home.

Mason bees overwinter in nesting cavities and spend at least 10 months going from egg to adult. These nesting cavities can be made out of bamboo sticks, hollow-stemmed plants like sunflowers, or holes drilled in wood. The holes should be 5/16" round and at least 6 inches deep. Mason bees live 4 to 6 weeks and finish laying eggs and pollinating by late spring. Inside the holes, the eggs are hatching, and the little larvae are consuming pollen. Generally, females are laid first and males last, as the males hatch first. In some insect hotels these nesting cavities are placed in old drainage tiles to keep them dry.

Carpenter bees hibernate as young adult females and males in hollow cavities.