Are bats roosting on a Ben Lomond home a sign of good luck or bad?

DR. JOAN: We have bats in the apex of the roof. They aren’t a bother, and we don’t see them very often. Sometimes the bats get turned around and crawl into the house. As a result, we leave the doors open, and they fly out!

Are they causing any damage to the house? We don’t want to hurt them because they are so delicate. Some people believe that bats bring good luck!

— Patty from Ben Lomond

DR. PATTY: While having bats in the neighborhood is beneficial, having them live in or on your home is not.

The most serious threat is rabies. Although it is unlikely that you will be bitten by a rabid bat, you may be exposed to rabies if you handle it with your bare hands.

Histoplasmosis, a lung infection caused by breathing in a fungus found in bat guano and bird droppings, is another, more common risk. Fever and cough are common symptoms, and it can last for months.

Guano can also cause structural damage to wood and other building materials, which can lead to roof leaks and other problems in the future.

Guano can accumulate anywhere bats roost, so you should hire an expert — this is not a do-it-yourself project — to remove it and block off the roosting areas. A professional can handle the bats without harming them and install exclusionary devices. The pupping season is coming to an end, but you’ll have to wait until early autumn to take action.

It is not recommended that you physically remove them if you want to try it yourself. Exclusion is your only viable option. You’ll need to figure out how they’re getting into the house and seal it off.

Hang shiny objects, such as old CDs, and install lights in those areas to deter them from roosting. Bats dislike the scents of cinnamon, eucalyptus, and peppermint.

We like bats in general, so consider putting up a bat house on your property, but not in your home.

DR. JOAN: I had never heard of or seen a tarantula hawk wasp in my 50 years of living in the East Bay. We’ve had them on our property for three years, and I see them when I ride my horse on Mount Diablo. I saw them in Tilden.

Knowing how painful their sting is, I’m naturally terrified of them, and they’re also creepy looking. How did they become so prevalent so quickly?

El Sobrante resident Linda Wuy

Although desert wasps are common in the Bay Area, they may be drawn there by the presence of tarantulas, which they use to incubate their young, and an abundance of food, which includes nectar, pollen, and the juice from fruits and berries.

They will sting if provoked, but they are not aggressive in general. Their sting is regarded as one of the most painful in the insect world; however, while the pain is intense, it subsides after about five minutes and is not fatal. You’re still wise to keep a safe distance from them.