A large spider appears to be drinking water off a plant during a downpour in late September 2020, after weeks of little rain. Credit: Aislinn Sarnacki / BDN

No one is saying that Maine residents should throw open their doors to invite outside critters to come inside, but some are actually pretty beneficial to have around the house.

And while creatures like spiders and bats are considered by some to be “creepy,” wildlife experts say they are just getting a bad rap and they really do more good than harm.

Nature’s bug controllers

When it comes to insect control, spiders and bats are natural exterminators.

“Spiders are mostly our friends,” said Dr. Kathy Murray, entomologist with the Maine Department of Agriculture, Conservation and Forestry. “They feed almost exclusively on insects so they are especially helpful with pest control in the garden or in the home.”

This time of year, for example, many Mainers are reporting infestations of ladybug-like insects known as the Multicolored Asian Lady Beetles, which are looking for warm places to spend the winter, but end up collecting on window interiors or room corners.

“When these insects look to come in for the winter, having a few spiders around can be helpful,” Murray said. “But honestly most [spiders] prefer being in the outdoors.”

The same can be said for bats.

“All of the bats that live in Maine are insectivores and have high metabolic rates, so they eat a lot of insects,” said Cory Mosby, fur-bearing small mammal biologist with The Maine Department of Inland Fisheries and Wildlife. “I have read one bat can eat 1,200 mosquitos a night or up to its weight in insects.”

While the bats’ diets include a wide array of insects, Mosby said a major item on the menu are moths, including that of the spruce budworm, a nemesis of the state’s forestry industry .

They also eat many of the insects which damage crops nationwide and Mosby said it is estimated the economic benefit from bats in terms of pest control as it relates to agriculture is $3.6 billion annually.

Keep calm and provide an exit

It’s important to note that healthy bats will generally avoid coming inside, Mosby said. He recommends if one is spotted in a house, people should consider an established “checklist” to ensure the human inhabitants’ health and safety, as well as that of pets.

So what happens if a bat gets into your home?

“Don’t freak out,” Mosby said. “Not only do they have good eyesight, bats have great echo-location so just open a window [or] a door, provide a clear path for them to get out and then just leave them alone.”

If left to its own devices, a bat will head for the nearest exit, Mosby said, adding that providing a clear path decreases the chances of human-bat contact, something that should be avoided.

“Bats can carry rabies,” he said. “If a bat does show up, ask yourself if there has been any exposure to pets or other residents in the home.”

If exposure — direct touching of or being bitten or scratched by a bat — is confirmed or suspected, the animal needs to be collected and tested for rabies, Mosby said. The best thing to do, he said, is to call the state’s rabies hotline at 1-800-821-5821.

“Someone there can direct you on what to do and who to contact to collect the bat,” Mosby said. “You may want to try a butterfly net or the shoebox-against-the wall trick, but all you are doing is alarming the bat and creating the possibility for exposure.”

That exposure risk is pretty low, Mosby stressed, with less than 1 percent of bats having the virus, but it should still be taken very seriously.

A colony of bats taking up residence in an attic or under the eaves can also set up conditions for the histoplasma fungus spores to grow as they thrive in back droppings — commonly referred to as guano.

“It really needs to be hotter and more humid than it gets in Maine for this fungus to show up,” Mosby said. “But you should still take precautions and wear proper gear to ensure you don’t inhale any spores if you are dealing with a bunch of bat guano.”

Eight-legged exits

While bats are able to get out on their own, spiders, according to Murray, may need a little help leaving the building.

“They can be gently escorted outside by using an inverted jar over the spider, slipping a piece of paper under the spider and then releasing it back outdoors,” she said. “If you have an issue where a lot of spiders are creating too many cobwebs in the house and being a nuisance, you can dispatch them sucking them up with a vacuum [but] they won’t survive that.”

All spiders, according to Murray, carry some degree of venom and will bite if provoked or startled. But she added none of the 400 species of spiders in Maine carry deadly venom.

If a poisonous spider is encountered, she said, it’s because it has hitched a ride into the state on imported foods or cargo coming in from the south.

“That’s why you should always wear gloves and take caution when reaching into dark spaces and holes on anything that has come in from down south,” she said.

Steps to prevent bats and spiders inside

Residents can lessen the odds of bats or spiders getting in by taking a look around the home and tackling some basic maintenance issues.

“Seal up any cracks you might have in foundations, exterior walls or around doors and windows where spiders could get inside,” Murray said. “And declutter [because] clutter provides great hiding places for spiders.”

Likewise with bats, cracks and crevices provide perfect entry points into a home and Mosby said they do not need a large opening.

“If a hole or crack is as wide as your pinky finger, a bat can get through it,” he said. “Anyplace where there is a hole to run a wire or pipe can provide access so make sure you seal around those.”

Julia Bayly

Julia Bayly is a reporter at the Bangor Daily News with a regular bi-weekly column. Julia has been a freelance travel writer/photographer since 2000.