If you’ve found a red spider in your house and are wondering what it is, you may need to take a closer look. Does the spider have a red body and legs or does it just have a red back? Is it tiny, small or quite large? Is it a jumping spider or something altogether more scary? Read about the characteristics and descriptions of the most common red spiders to see which arachnid you’ve found.
Tiny Red Spiders
If you’ve come across some very small red spiders, they are most likely clover mites. Mites are a type of arachnid and the clover mite is smaller than a pinhead. They can be found in large numbers across the US and can infest homes looking for food or shelter. While not dangerous to humans or to the structural integrity of your home, they leave a bright red stain when squashed and may be difficult to control.
Clover Mites
Scientific name: Bryobia praetiosa
Size: Between 0.75 and 0.85 mm (0.030–0.033 in) long
Distinguishing features: Younger mites and eggs are bright red. Adults have a long pair of front legs.
Habitat: Clover mites are usually found in healthy grass lawns and on sun-exposed walls across the world.
Dangerous to humans?: No. They might be annoying and cause staining to fabrics and floors but they are not dangerous.
How to get rid of clover mites: To stop clover mites from infesting your home, trim grass back if it comes up to the door or walls. Use miticide treatments for barrier protection. If the red clover mites are already inside, vacuuming them up is the easiest way to get rid of them, although take care to avoid crushing them as they will leave red stains behind.
Spiders With a Red Body
Although there are a couple of spiders that might fit this description, the most common red- bodied spider is the woodlouse spider. Getting its name from the fact that it predominantly eats woodlice, this bright red to dark red spider can look quite menacing due to the large fangs protruding from its mouthparts. It can be beneficial in the garden as it doesn’t eat plants, only pests. You probably don’t want to see these red spiders inside your home, however, as they can have a nasty bite.
Red house spiders also fall into this category, and while they are found in some parts of the US, they’re not generally found in the western states.
Woodlouse Spider
Scientific name: Dysdera crocata
Size: Adult females can grow to a body length of 11–15 mm (0.43–0.59 in).
Distinguishing features: This red house spider has large, powerful mouthparts or “chelicerae” and does not spin webs to catch food.
Habitat: Leaf litter and human houses, primarily across the northern hemisphere.
Dangerous to humans?: No. The red woodlouse spider is poisonous and can and will bite humans if threatened but the amount of venom it can inject is not large enough to be harmful to humans. Some itching at the bite site may occur but shouldn’t last very long. If you happen to be allergic to spider venom, however, contact a medical professional if you have trouble breathing or a lesion appears at the bite area.
How to get rid of woodlouse spiders: Prevent red spiders coming into your house by sealing up exterior cracks and gaps, especially around windows. Install a tight-fitting door sweep and remove potential nesting sites such as plants and trash cans from around exterior entrances. In the case of a large number of red spiders around your home, contact a local pest control company.
Red House Spider
Scientific name: Nesticodes rufipes
Size: The larger female can have a body length of 5-8 mm (0.2 – 0.3 in).
Distinguishing features: The rounded abdomen of the red house spider can mean it’s sometimes mistaken for a type of black widow.
Habitat: Houses and yards, most commonly in California, Texas and Florida.
Dangerous to humans?: No. Red house spiders can bite humans but their venom is non-toxic meaning that bites should not require any special medical attention.
How to get rid of red house spiders: Frequent dusting of corners, door frames and clearing clutter will discourage red house spiders from taking up residence in your home. Seal up any cracks in the exterior of your house to prevent them from coming inside. If you have any sort of red house spider infestation, contact a professional pest control company.
Spiders With Red Markings
Most commonly, there are two species of spider with red markings on them. One is the Johnson’s jumping spider which has a bright red abdomen. The other is the black widow which has a distinctive red hourglass shape on its abdomen. It’s important to be able to tell the difference between these two red backed spiders as the black widow is notorious for its potentially dangerous bite.
Red-Backed Johnson’s Jumping Spider
Scientific name: Phidippus johnsoni
Size: Males and females grow to approx. 10mm (0.4 inches) in body length
Distinguishing features: This black spider has a bright red back with the male having a solid red abdomen and the female having a black stripe on a red back.
Habitat: Generally found between the Pacific coast and the Rocky Mountains. The red backed jumping spider prefers dry woodlands or coastal dune habitats.
Dangerous to humans?: No. Not to be confused with the actually venomous “redback spider” (Latrodectus hasselti), these red back jumping spiders are not venomous to humans. In the unlikely event of a bite, you will not need medical attention.
How to get rid of red-backed jumping spiders: If you find a lot of jumping spiders inside your home, vacuuming them up is the easiest way to get rid of them. Otherwise, a pest control company can treat your property with preventive barrier sprays.
Black Widow
Scientific name: Latrodectus hesperus – the Western black widow
Size: Females can grow to 14–16 mm (0.5 in) in body length
Distinguishing features: This spider is shiny black with a bulbous abdomen and the famous bright red hourglass shape, although this can sometimes also be white or yellow.
Habitat: This species of black widow is found throughout western North America.
Dangerous to humans?: Yes. The black widow is highly venomous and symptoms from a bite can range from mild irritation to a severe reaction. Female black widow venom acts as a neurotoxin to humans so seek medical advice if you have been bitten by a black widow spider.
How to get rid of black widow spiders: If you see black widow spiders in your home or yard, you can contact a professional pest control company to remove them. To stop them from entering your home, install tight-fitting door sweeps, seal up any holes or cracks in the exterior of your home and remove potential hiding spots by getting rid of clutter in your yard and garage.
