If you’ve spotted a black and red bug in Ohio, you’re most likely looking at one of five common species: the boxelder bug, the large or small milkweed bug, the red-shouldered bug, or a spotted lanternfly nymph. All share that distinctive black-and-red color pattern, but telling them apart matters, especially since one is an invasive pest that Ohio has placed under statewide quarantine.
Boxelder Bugs
Boxelder bugs are the most common black and red bug Ohioans encounter, particularly in fall when they cluster on the sunny sides of buildings looking for a warm place to spend winter. Adults are about half an inch long and grayish-black with three red stripes behind the head, red lines along the outer edges of the wings, and a red margin on the front half of the wings. The young nymphs are smaller, wingless, and tend to show even more red than adults.
These bugs feed primarily on boxelder trees (a type of maple), though they’ll also use other maples and ash trees. They don’t bite, don’t transmit diseases, and don’t damage your home’s structure. Their main offense is being annoying in large numbers and occasionally leaving small stains on light-colored surfaces.
Large and Small Milkweed Bugs
If you found the bug on or near milkweed plants, it’s likely a milkweed bug. Ohio has two species. The large milkweed bug has a bold orange-red and black banded pattern across its back and grows to about three-quarters of an inch. The small milkweed bug is closer to half an inch and has a red X-shaped marking on its back, sometimes with a heart-shaped black patch in the center.
Both species feed mainly on milkweed seeds and seed pods, piercing them with needle-like mouthparts to suck out the contents. They’ll also feed on other plants in the dogbane family, including butterfly weed, climbing milkweed, and tropical milkweed. The small milkweed bug is less picky as an adult and may feed on a wider range of plants or even dead insects.
One key difference: large milkweed bugs migrate south for winter, similar to monarch butterflies. Small milkweed bugs stay put and overwinter in Ohio. Neither species bites or poses any risk to people or pets. If you’re growing milkweed to support monarchs, these bugs can reduce seed production, but they rarely harm the plants themselves.
Red-Shouldered Bugs
Red-shouldered bugs look strikingly similar to boxelder bugs and are often mistaken for them. Both are about half an inch long, grayish-black, and have red eyes. The quickest way to tell them apart: red-shouldered bugs have only two red stripes behind the head and no red markings on the wings. Boxelder bugs have three red stripes and noticeable red on the wings.
Red-shouldered bugs feed on seeds from golden rain trees and other plants. Like boxelder bugs, they sometimes gather on buildings in fall but are generally less of a nuisance. They don’t bite or cause property damage.
Spotted Lanternfly Nymphs
This is the one to watch for. The spotted lanternfly is an invasive pest first found in Ohio in 2020, and as of February 2026, the entire state is under quarantine. The adults are gray and red moths that look nothing like the other bugs on this list, but the nymphs are easy to confuse with other black and red insects.
Spotted lanternfly nymphs hatch in April and go through four stages. The first three stages are small (starting at about an eighth of an inch), black with white spots, and no red at all. By the fourth stage, usually around June, the nymph turns red with white dots and black stripes and reaches about half an inch long. That fourth-stage nymph is the one most likely to be mistaken for a milkweed bug or boxelder bug.
The key difference is the white spots. No other common Ohio black-and-red bug has prominent white dots scattered across its body. Spotted lanternflies also tend to congregate on tree-of-heaven, grapevines, maples, and fruit trees rather than milkweed. If you find what you believe is a spotted lanternfly on public property, report the infestation to the property owner or responsible party, such as a park manager or municipal office.
How to Tell Them Apart at a Glance
- Three red stripes behind the head, red on wings: boxelder bug
- Two red stripes behind the head, no red on wings: red-shouldered bug
- Orange-red and black bands, found on milkweed: large milkweed bug
- Red X-shape on back, smaller, found on milkweed: small milkweed bug
- Red with white dots and black stripes (summer): spotted lanternfly nymph
Do Any of Them Bite or Cause Harm?
None of Ohio’s common black and red bugs bite humans or pets. Boxelder bugs, milkweed bugs, and red-shouldered bugs are all “true bugs” with piercing mouthparts designed for plant tissue and seeds, not skin. They won’t sting, and they aren’t venomous.
You may have also noticed tiny red mites on patios, sidewalks, or windowsills. These are sometimes confused with chiggers, but they’re a completely different creature. Those larger red mites you can see with the naked eye don’t bite humans at all, though they can leave a red stain if you crush them. Actual chiggers are microscopic and yellowish, essentially invisible without magnification.
The spotted lanternfly is the only species on this list that causes real economic damage. It feeds on the sap of over 70 plant species and poses a serious threat to vineyards, orchards, and hardwood trees.
Keeping Black and Red Bugs Out of Your Home
Boxelder bugs are by far the most likely to invade Ohio homes. They don’t breed indoors or cause structural damage, but hundreds clustering in your walls and emerging on warm winter days gets old fast. Prevention is the most effective strategy, and the work needs to happen before the end of August, before the bugs start seeking shelter.
Seal every opening you can find. Repair or replace damaged window and door screens. Caulk gaps around utility lines, pipes, outdoor faucets, and dryer vents. Install door sweeps on all exterior doors and a rubber seal along the bottom of garage doors. For brick or stone exteriors, check for cracks an eighth of an inch or larger and seal them with silicone or elastomeric caulk. Don’t seal weep holes at the base of brick veneer walls; instead, use ventilation plugs from a hardware store.
If you already have boxelder bugs inside, vacuum them up or sweep them into a dustpan. Spraying insecticides indoors isn’t effective because the bugs don’t live long once they’ve emerged into your living space. If you’ve had repeated invasions, an exterior insecticide treatment applied in late summer or early fall, when bugs first start clustering on your walls, can reduce the numbers that make it inside. For severe infestations, a professional pest control service will have better equipment and products than what’s available over the counter.
Milkweed bugs and red-shouldered bugs occasionally wander indoors but almost never in large enough numbers to be a problem. The same sealing measures that keep boxelder bugs out will work for them too.