“Red spider” is a common term that can cause concern for many people. Many arachnids are commonly referred to as “red spiders,” encompassing a diverse group from harmless mites to true spiders. This general term does not denote a scientific classification, and most red-colored creatures pose little threat to humans.
Understanding Venomous Versus Poisonous
A key distinction is the difference between venomous and poisonous. Venomous animals inject toxins into another organism, typically through a bite or sting. Spiders are venomous, delivering toxins through fangs. The venom can affect various bodily systems.
Conversely, poisonous organisms release toxins when touched or ingested. For instance, a poisonous frog secretes toxins through its skin. The crucial difference lies in the delivery method: venom requires an active injection, while poison is passively transferred. The molecules in venom are generally too large to be absorbed through intact skin, necessitating a wound for entry.
Common Red Arachnids You Might Encounter
Many small, red arachnids are frequently mistaken for dangerous spiders but are generally harmless. Clover mites (Bryobia praetiosa) are tiny, reddish-brown pests, smaller than a pinhead. They do not bite humans or transmit diseases.
Another common arachnid is the woodlouse spider (Dysdera crocata), identifiable by its dark-red body and legs, with a shiny, pale abdomen. These nocturnal hunters do not build webs for prey capture, instead using their prominent fangs to hunt woodlice. While they can bite if provoked, their venom is not considered medically significant to humans, typically causing only mild, localized irritation. Similarly, some common house spiders may exhibit red coloration or markings but are not dangerous.
Truly Dangerous Red or Red-Marked Spiders
While most red arachnids are not a threat, a few species with red markings are medically significant. Black widow spiders (Latrodectus species) are recognized by a distinctive red hourglass marking on the underside of their shiny black abdomen. Females are generally larger than males and are the only ones capable of delivering a dangerous bite. Their venom contains neurotoxins that can cause severe pain, muscle cramping, nausea, and sweating.
The redback spider (Latrodectus hasselti), a close relative of the black widow, is found predominantly in Australia and has a prominent red stripe on its upper abdomen, along with an hourglass-shaped red mark underneath. Its neurotoxic venom can cause severe pain, sweating, and systemic symptoms, though fatalities are rare due to available antivenom. The red widow spider (Latrodectus bishopi), found in limited regions, also possesses potent venom. These spiders typically bite only when provoked or if their web is disturbed.
What to Do After a Spider Encounter or Bite
Preventing spider bites involves simple precautions like shaking out clothing and shoes before wearing them and wearing gloves when working in areas where spiders might hide, such as woodpiles or garages. Sealing cracks and crevices in the home can also deter spiders from entering. Reducing clutter indoors and keeping bedding away from walls minimizes hiding spots.
Should a spider bite occur, initial first aid involves cleaning the wound with mild soap and water. Applying a cool compress or ice pack to the bite area for 15 minutes each hour can help reduce pain and swelling. Elevating the affected area is also recommended. Over-the-counter pain relievers can manage discomfort, and antihistamines may help with itching. Medical attention should be sought if symptoms worsen, if there are signs of infection, or if a bite from a black widow or similar dangerous spider is suspected.