How to Control Wasps in Bat Houses

Wasps in bat houses can coexist with bats as long as they don't become to numerous and close off the chambers.

Mud Dauber Wasps

As the name implies, mud daubers use mud to build nests that resemble long tubes. Mud daubers are solitary hunting wasps (family Sphecidae) that build nests on, or in, buildings, under bridges, in crevices, or on rock faces.

Nests contain eggs along with paralyzed insects and spiders on which the developing larvae feed. Left unchecked, mud daubers can fill virtually all of the roosting space in a bat house with nests, leaving little room for bats.

You want to check your bat house two or three times a year for a wasp nest. The best way is to wait till late day around dusk when the bats are gone. Use a strong flashlight and look up into the bat house to see if there are any nests in the the chambers. You must make sure that all pups are gone from the house also. If they are not then just wait a couple more weeks and make another inspection

Repeat this process till you do not see any pups in the house. If you do see a wasp nest do NOT USE any wasp repellent spray as the spray mist will penetrate the wood and most likely the bats will not stay within their home.

Before starting to clean out the bat house you want to wear some protective clothing. A long sleeve shirt, stocking cap or hat and goggles. There are a couple different ways to clean out the nest from the bat house. You can leave the house where it is mounted and work from a extention ladder with a long narrow stick to scrape out all of the nesting material. For safety reasons you want to have someone holding the ladder steady for you.

The other option would be to mount your bat house on a steel pole and set it up with our Easy-up-Mounting bracket so the bat house can be raised and lowed at any given time for inspection and maintenance.

You will see that all of our bat house chambers are designed with 3/4" spacing to help eliminate the issues of Mud Daubers building a nest in your bat house you purchased from

This is a great story below of why you need to make inspections and clean out your bat house when needed.

In 1997, Carol and Baxter Adams had 200 free-tailed bats in their back-to-back pair of nursery houses. In June 1998, however, they noticed few bats using the houses. We inspected the houses and observed that the roosting chambers had become so clogged with mud dauber nests that only five bats remained.

After dark, when the bats were gone, we removed all of the nests with a yardstick. By the next morning, to our surprise, 50 bats had already returned. The following day 50 to 100 bats were back, and there were more than 350 just one month later. By this time, there was little room for mud daubers to return.

Paper Wasps and Red Wasps

Paper or red wasps (family Vespidae), the social wasps) use a mixture of wood pulp and saliva to construct nests, which hang from a stem-like pillar. In bat houses, nests are typically built at the top of the roosting chambers, especially where a gap is left between the roof or ceiling and the partitions. When bats and wasps occupy bat houses at the same time, they may segregate into separate roosting chambers, as bats can be killed by wasp stings.

© Bat Conservation International, Inc.
Used with Permission.

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