Month by Month: Pests to Expect in Indianapolis

Which pests are active in Indianapolis each month?

Every month brings a different set of pests in Indianapolis. Winter is mostly indoor trouble, spring brings termite swarms and ants, summer belongs to mosquitoes, ticks and wasps, and fall sends mice and overwintering bugs looking for gaps in the house. The table below lays out the full year for the east side.

Timing in the table is typical, not fixed. A warm March can bring termite swarmers out early, a wet June can turn every clogged gutter into a mosquito nursery, and a mild November keeps lady beetles crawling on sunny siding well past the first frost.

Use the right-hand column as a to-do list. Much of the cheapest pest work in Indianapolis happens a month before a pest shows up, not after.

What do Indianapolis homeowners deal with in winter?

Winter in Indianapolis is mostly an indoor season. Mice that slipped in during fall nest in walls, attics and basements, and boxelder bugs and Asian lady beetles hiding in wall voids wander into living space on sunny afternoons. German cockroaches and bed bugs carry on as usual, because a heated building never really gets cold.

January is usually the snowiest month here, and that cold is what keeps mice indoors once they have found a way in. Scratching above a bedroom ceiling or fresh droppings behind the stove in midwinter often means the entry point is still open.

Overwintering bugs that crawl out in February are not a new invasion. They went into the walls last fall and are stirred up by furnace heat or a sunny window. Vacuuming them is the cleanest fix; sealing waits until late summer, before the next wave.

Holiday travel is a common way bed bugs come home. Check suitcase seams and the mattress edges in any hotel room, and unpack straight into the washer and a hot dryer.

When do termites swarm in Indianapolis?

Eastern subterranean termites in central Indiana swarm mainly from March through May, usually on a warm day and often soon after rain. April is a common month for both winged termites and winged ants. A swarm inside the house, especially in a basement, is a strong sign that a colony is working in or under the structure.

Swarmers are the colony's winged reproductives. They flutter toward light, drop their wings within minutes and die indoors without reaching soil, so the swarm itself does no damage. The workers doing the damage stay hidden in soil, mud tubes and the wood itself.

Spring is also carpenter ant season under Irvington's big old shade trees, and the two are easy to confuse. The termite guide shows how to tell them apart, and a termite inspection settles the question if you find wings on a sill.

Odorous house ants and pavement ants wake up in April and May as well. A trail along a kitchen counter after a spring storm is usually one of those two, not termites.

When is mosquito season in Indianapolis?

Mosquitoes in Indianapolis are active roughly from May through September, and a warm fall can stretch the season into October. Numbers jump after heavy rain near creeks, retention ponds and clogged gutters. West Nile virus usually turns up first in Marion County mosquito samples in July, so July and August call for extra care at dusk.

The Marion County Public Health Department runs a county-wide mosquito control program that monitors mosquitoes for West Nile virus, treats breeding sites and educates residents. What happens in your own yard still depends on what you do with buckets, tarps, old tires and gutters.

Old houses add their own breeding spots. Box gutters and downspouts on Victorian and Craftsman homes clog with seeds and leaves, and yards that slope toward Pleasant Run or Pogue's Run can hold puddles for days after a storm.

The CDC's advice is simple: use an EPA-registered repellent, cover up between dusk and dawn, and keep window screens in good repair. In the yard, tip out standing water at least once a week. For heavy pressure, mosquito control runs as a monthly visit through the season.

When are ticks most active around Indianapolis?

Ticks around Indianapolis are active from early spring through late fall on mild days. Blacklegged ticks, which can carry the bacteria behind Lyme disease, have been found in nearly every Indiana county. American dog ticks are common in grassy areas, and the ehrlichiosis risk tied to lone star ticks is highest in southern Indiana.

The Indiana Department of Health reports most human Lyme disease cases from the northwest and west-central parts of the state, but that is no reason to skip tick checks here. The woods along Fall Creek in Fort Harrison State Park, wooded lots in Meridian Hills and the field edges of Franklin Township all hold ticks.

The CDC recommends treating boots and clothing with 0.5% permethrin, checking your whole body after time outdoors, showering within two hours and tumbling dry clothes on high heat for 10 minutes. Around the house, keep grass short and lay a 3-foot strip of wood chips or gravel where lawn meets woods.

Where a yard backs onto woods or a creek, a tick yard treatment along the edges cuts down on the ticks the dog brings inside.

What should you watch for in late summer?

Late summer is stinging-insect season in Indianapolis. Yellowjacket, wasp and bald-faced hornet colonies are at their largest by August, tucked under eaves, inside sheds, in wall voids and in the ground. Fleas peak on pets and in shady yards, and it is a good time to watch for spotted lanternfly.

Ground-nesting yellowjackets are the ones people step on, often while mowing or pulling weeds along a fence. A nest the size of a basketball under a porch roof or inside a carriage house gable is a job for wasp and hornet removal, not a can of spray from the top of a ladder.

Spotted lanternfly has turned up in several Indiana counties since 2021, starting in Switzerland County in the southeast and later in northern counties, but it had not been confirmed in the Indianapolis area as of 2026. Check the Indiana DNR's current map, and report a sighting to the DNR Division of Entomology & Plant Pathology at 866-NO-EXOTIC (866-663-9684). It is a reporting matter, not a pest control service.

Why do pests move indoors in the fall?

Cold nights push pests toward the warmth of houses. House mice start moving inside in September and keep coming through November, and boxelder bugs, Asian lady beetles and brown marmorated stink bugs crowd onto sunny south and west walls in September and October, hunting for cracks to spend the winter in.

Fall is also when fields around Franklin Township, New Palestine and McCordsville are harvested and the cover there thins out. Homes at the edge of those fields often find mice in the garage first.

The work that pays off happens in late August and early September: sealing utility gaps, screening attic and soffit vents, fitting door sweeps and getting a perimeter treatment for fall invaders on before the first cold snap. The guides on mice in fall and boxelder bugs, lady beetles and stink bugs go step by step.