Indiana is home to a wide mix of insects and arachnids, from harmless nuisance species to a handful that can pose real health risks. Whether you’re hiking southern woodlands, mowing a suburban lawn, or tending a garden, knowing which bugs are common in the state helps you avoid the ones that matter and stop worrying about the ones that don’t.
Ticks: Indiana’s Top Outdoor Concern
The most frequently encountered tick in Indiana is the American dog tick, also called the eastern wood tick. It’s the primary carrier of Rocky Mountain spotted fever in the United States and can transmit the bacteria through every stage of its life cycle, from larva to adult. You’ll find it in grassy and wooded areas statewide, and it’s most active from April through August.
The lone star tick turns up mainly in wooded areas across the southern half of the state. Females are easy to identify by a single white dot on their back. This species is aggressive and feeds on almost anything, including people. It has been loosely linked to tularemia, Rocky Mountain spotted fever, and Lyme disease, but it is not considered an important carrier of any of those illnesses. Its bite can, however, trigger a red-meat allergy known as alpha-gal syndrome in some people.
The deer tick (black-legged tick) is the one to watch most carefully. It is the primary carrier of Lyme disease, which has spread to 43 states since it was first identified in 1975. Lyme disease is most prevalent in the Northeast and Upper Midwest, and Indiana falls within that range. Deer ticks are small, dark brown, and lack any white markings, making them harder to spot than other species. After spending time in tall grass or wooded areas, a full-body tick check is the single most effective way to reduce your risk, since the bacteria generally need 24 to 36 hours of attachment to transmit.
Mosquitoes and West Nile Virus
Indiana’s mosquito season runs roughly from late spring through early fall, peaking in the humid months of July and August. The species that matter most from a public health standpoint belong to the Culex group, which are the primary carriers of West Nile virus in the state. These mosquitoes breed in stagnant, often polluted water: storm drains, old tires, birdbaths, and clogged gutters.
Indiana reports West Nile cases every year, though the numbers vary widely. In 2010, a representative year for surveillance data, the state recorded 13 human cases and 328 positive mosquito pools (batches of up to 100 mosquitoes tested together). Nearly every positive pool involved Culex mosquitoes. The vast majority of Indiana’s human cases that year came from the northern tier of counties, and almost all were documented between late July and mid-September with a peak in August. Most people infected with West Nile never develop symptoms, but a small percentage experience fever, headache, and body aches, and a fraction of those progress to serious neurological illness.
Venomous Spiders
Only two spider species in Indiana can cause serious injury: the brown recluse and the black widow. Neither is aggressive, and bites from either are quite rare according to the Indiana Department of Natural Resources.
Brown recluse spiders prefer dry, undisturbed spots like barns, sheds, closets, and storage boxes. They’re tan to brown with a violin-shaped marking on the head region. Their venom can cause a slow-healing skin wound, but serious complications are uncommon. Black widow spiders stick to undisturbed outdoor locations and are rarely found inside homes. Females are glossy black with a red hourglass on the underside and build irregular webs near ground level.
Reactions to bites from either species depend on the amount of venom injected, the person’s age, overall health, and individual sensitivity. Fatalities from spider bites are extremely rare. Severe pain, trouble breathing, dizziness, or nausea after a bite warrants prompt medical attention.
Stinging Wasps, Hornets, and Yellowjackets
Indiana has several social wasp species, and they all follow the same annual pattern: a queen starts a new colony in spring, the colony grows through summer, and activity peaks in late summer and early fall before the colony dies off with the first hard frost. No colony reuses a nest from a previous year.
Paper wasps are the slender, long-legged wasps you see under eaves and porch ceilings, building small open combs. The European paper wasp has become very common in Indiana and likes to nest inside enclosed spaces: light fixtures, bird boxes, gas grills, and boats. Baldfaced hornets are large, black-and-white insects that construct the big grayish, pear-shaped nests you sometimes spot hanging in trees. By late summer a single colony can hold close to a thousand workers.
Ground-nesting yellowjackets are responsible for many painful encounters. Several species build underground nests along creek banks, in lawns, garden beds, and forest floors. Late-season colonies can reach a few thousand workers, making an accidental step on a hidden nest a serious problem. The German yellowjacket and the European hornet sometimes nest inside wall voids, attics, and basements instead. By late summer, yellowjackets often scavenge for sugar and meat, which is why they swarm picnics and outdoor cookouts in August and September.
Invasive Species to Watch For
The spotted lanternfly is Indiana’s newest high-profile invader. A population was first confirmed in Switzerland County near the Ohio River in July 2021. Since then, infestations have been found in Huntington, Elkhart, St. Joseph, and Porter counties. This insect feeds on more than 70 plant species, including grapevines, fruit trees, and hardwoods, and poses a significant threat to agriculture and forestry. State and federal agencies are still surveying to determine how far it has spread and what management strategies to deploy.
The emerald ash borer, which arrived in the Midwest in the early 2000s, has already killed tens of millions of ash trees across the region. Indiana has been heavily affected, and the insect is now present in every county. If you have ash trees on your property, preventive treatment is the only reliable way to keep them alive once the borer is in your area.
If you spot what you believe is an invasive insect, the Indiana DNR asks you to photograph it and report the sighting through the EDDMapS website or the GLEDN smartphone app. You can also call the state’s invasive species hotline at 1-866-663-9684 or email depp@dnr.IN.gov for terrestrial species.
Common Crop and Garden Pests
Indiana sits in the heart of the Corn Belt, and its farms and home gardens share a roster of insect pests. Bean leaf beetles chew holes in soybean foliage and can transmit bean pod mottle virus. Japanese beetles, recognizable by their metallic green bodies and copper wings, feed on more than 300 plant species and are a persistent summer headache for gardeners. Potato leafhoppers cause “hopper burn,” a browning and curling of leaves on beans, alfalfa, and potatoes. Grasshoppers, especially the redlegged and differential species, can flare up in hot, dry summers and strip foliage from row crops and garden plants alike.
Slugs have become an increasing concern on Indiana farms that use conservation tillage, where crop residue left on the soil surface gives slugs the cool, moist habitat they thrive in. The gray garden slug and marsh slug are the most common culprits, feeding on young soybean and corn seedlings in spring. In home gardens, handpicking at night, reducing mulch near seedlings, and iron phosphate baits are the most practical controls.