Tiny red bugs: clover mites, velvet mites, chiggers and the others, and which ones bite

Something very small and very red is walking across the window sill, or the patio, or your sock after a walk through long grass. Red is a loud colour on a tiny animal, and it makes people nervous. Most of the time it should not. Of the half-dozen usual suspects, only one group is known for biting people, and it is the one you are least likely to actually see.

First, count the legs

Hold a phone camera close or use a magnifier. Eight legs means a mite, which is an arachnid, a relative of spiders and ticks rather than an insect (more on the difference in are spiders insects?). Six legs and a body in sections means an insect, and the tiny red insects are almost always the young of something bigger. Mites also have no visible waist: the body is one round blob with legs.

Clover mites: the red dots on the window sill

If you have dozens or hundreds of tiny red specks crawling over a sunny wall, sill or window frame, it is almost certainly clover mites. They are smaller than a pinhead, bright red to rusty brown, and their front pair of legs is much longer than the others, which makes them look as if they are feeling their way forward.

They live in lawns and feed on grass, clover and other low plants. Spring and autumn are when they wander, and a warm south- or west-facing wall next to a lawn is the classic spot. They do not bite people or pets, they do not eat anything indoors, and they do not breed inside. The only harm they do is the red smear when someone squashes them.

What helps:

• Do not crush them. Vacuum them up or wipe gently with a damp cloth.
• Make a gap. A strip of bare soil or gravel along the base of the wall, where grass used to touch it, gives them little reason to climb.
• Close the way in. Gaps around window frames are their door.

Velvet mites: the red cushion on the path

The red velvet mite, card #167, is the big one: a few millimetres long, plump, and covered in fine hairs that make it look like a scrap of red velvet. You usually see it walking across soil, moss, stones or a garden path, often after rain in spring and early summer.

It is a predator, and a useful one. Adults eat small insects and insect eggs in the soil and leaf litter. The young hatch as tiny larvae that ride on insects and other small creatures and feed on them before dropping off. People are not on the menu. The bright red is generally thought to be a warning to birds and other predators that the mite tastes bad.

Leave it where it is. If it has wandered somewhere it will get stepped on, move it to the nearest flower bed on a leaf.

Chiggers: the ones you will not see

Chiggers are the larvae of harvest mites, and they are the reason “which ones bite” is a fair question. In Britain the common species is simply called the harvest mite; in France, the aoûtat. The larvae are so small that most people never see one: a red or orange dot at the very edge of eyesight, in long grass, scrub and woodland edges, mostly from mid-summer into early autumn.

The larvae climb onto passing animals, including people, and feed briefly through the skin before dropping off. Contrary to a widespread story, they do not burrow into the skin and they do not stay there. The adults are a different matter: velvety red mites, related to velvet mites, that live in the soil and eat small invertebrates.

You cannot tell what caused a mark on your skin from a guide like this one, and neither can we. If something on your skin worries you, ask a doctor or a pharmacist. For prevention, the usual advice is long trousers tucked into socks in long grass, and a shower and a change of clothes after a walk through it.

The others

• Spider mites. Tiny red or greenish mites on houseplants and in greenhouses, with fine webbing between leaves and pale speckling on the leaf surface. A plant problem, not a people problem. Isolate the plant, rinse the leaves, raise the humidity; predatory mites sold for biological control are another option.
• Boxelder bug nymphs. Bright red, six-legged, with black legs, clustering on sunny walls in North America in autumn alongside the black-and-red adults. Card #111.
• Firebug nymphs. Red with black spots, in groups at the base of lime and mallow plants in Europe, looking like smaller, wingless versions of the adults. Card #113.
• Milkweed bug nymphs. Orange-red with dark wing pads, in clusters on milkweed pods. Card #112.
• Red aphids. Some aphids, including pink and red forms of the green peach aphid, cluster on stems and buds. Plant sap feeders.
• Red imported fire ants. Small reddish-brown ants from a domed soil mound, pouring out fast when it is disturbed. Not a mite, and the one red bug here that stings. Card #22, which has a red safety level in the Field Guide.

Front desk note: the red on a crushed clover mite is not blood. People see a red smear on the sill and assume they have been bitten. They have not; the mite was simply red all the way through.

Which ones bite

If you are still not sure which red dot you have, a sharp close-up in the identifier gives a name with a confidence level and a safety read, and the spiders, ticks and mites section of the Field Guide has the velvet mite and its relatives.