Overview
The Spitting Spider (Scytodes thoracica) is a small, slow-moving, and biologically extraordinary nocturnal arachnid belonging to the family Scytodidae. Native originally to the rocky Mediterranean basin and temperate Europe, this gentle domestic companion has hitched rides with human commerce to every continent on Earth, becoming one of the most famous and beneficial household micro-predators in the animal kingdom. Clad in a distinctive pale yellow to amber body decorated with intricate, dark brown-to-black mottled markings that resemble Chinese calligraphy or leopard spots, it is instantly recognized by its bizarre, high-domed, humpbacked carapace.
What makes Scytodes thoracica a world-renowned marvel of evolutionary biomechanics is its completely unique, projectile-hunting superpower: it is the only spider in the world that hunts by spitting pressurized venomous silk at its prey. Creeping up on silverfish or moths under the cover of darkness with agonizing stealth, when it closes within ten to twenty millimeters, it fires two twin zig-zag jets of sticky, venom-laced silk from its fangs in a fraction of a millisecond. The twin streams oscillate thousands of times per second, pinning the victim to the wall in an instantaneous silk straightjacket before the prey can react. Completely harmless to humans, the spitting spider is a celebrated marvel of nature’s biochemical weapons.
AT A GLANCE
- Common Name: Spitting Spider
- Scientific Name: Scytodes thoracica
- Category: Invertebrates
- Subcategory: Arachnids
- Size: Body length: adult females 4–6 mm (0.16–0.24 in); adult males 3–5 mm (0.12–0.20 in); leg span 15–20 mm (0.6–0.8 in)
- Weight: 8–20 mg (0.00028–0.00071 oz)
- Lifespan: 2–4 years in the wild; females can live up to 5 years
- Diet: Carnivorous nocturnal pursuit predator feeding on silverfish, moths, booklice, houseflies, mosquitoes, and other spiders (including venomous recluse spiders)
- Habitat: Warm human dwellings, basements, stone cellars, attics, libraries, and naturally under rocks, caves, and bark in Mediterranean climates
- Range: Cosmopolitan, natively Palearctic across Europe, northern Africa, and temperate Asia; widely introduced and established globally throughout North America, South America, Australasia, and southern Africa
- Conservation Status: Not Evaluated
Biology and Physical Characteristics
Morphologically, Scytodes thoracica is built entirely around its revolutionary projectile artillery system. Its cephalothorax is enormous, arched, and high-domed, sloping steeply down toward the abdomen. This massive head vault is necessary because it houses colossal, specialized venom glands that occupy more than half of its entire cephalothoracic volume. Unlike ordinary spiders whose venom glands produce only digestive toxin, the spitting spider’s venom gland is bifurcated into two distinct physiological chambers: an anterior chamber that synthesizes neurotoxic and proteolytic venom, and an immense posterior chamber that manufactures sticky, fast-drying liquid silk proteins. Its six small, dark eyes are arranged in three distinct pairs (dyads). Its legs are extraordinarily long, slender, and pale, banded with dark rings, walking with a slow, deliberate, stilt-like gait that generates zero ground vibrations.
Behavior and Ecology
Behaviorally, spitting spiders are strictly nocturnal and solitary, spending daylight hours hidden behind baseboards, inside book crevices, or beneath cellar stones. At night, it hunts with methodical patience, using its ultra-sensitive, elongated front legs to detect the air currents and vibrations of moving silverfish. When within spitting range (roughly one to two centimeters), it fires: contracting specialized cephalothoracic muscles, it shoots two streams of silk-venom mixture through microscopic nozzles in its chelicerae at velocities exceeding twenty meters per second. As the jets emerge, the chelicerae oscillate rapidly side-to-side, causing the liquid to cross and form an overlapping zig-zag net that contracts and solidifies on contact, gluing the struggling insect to the surface in less than twenty milliseconds. The spider then walks up calmly, bites the immobilized prey to inject venom, and feeds. Females exhibit dedicated maternal care, carrying a spherical silk egg sac containing 20 to 30 eggs held securely in their jaws for weeks until the spiderlings hatch.
Conservation and Human Impact
The Spitting Spider has not been formally evaluated (Not Evaluated) by the IUCN Red List of Threatened Species, though it is universally recognized by arachnologists as globally secure, abundant, and widespread. As an obligate synanthrope in temperate regions, it flourishes in indoor human habitats, where it provides invaluable biological pest control by hunting nuisance insects such as silverfish, carpet beetles, and clothes moths. In warmer Mediterranean and subtropical zones, it is celebrated for hunting and killing dangerous brown recluse spiders (Loxosceles), which it safely pins down from a distance without entering striking range.
Interesting Factoid
The spitting spider is like a real-life comic book superhero—it shoots two twin streams of venomous spider-silk from its fangs that wiggle back and forth like lightning bolts, gluing its prey to the wall in less than 20 milliseconds before the bug even knows what happened!