**Red-backed Spiders** (*Latrodectus hasselti*) are highly venomous spiders native to Australia and are related to the Black Widow spiders (*L. mactans*). They are small, black, and notorious for the distinct, bright **red stripe** visible on the top of the female’s abdomen. The conflict is **medically significant venom**: the female’s bite is venomous and can cause severe pain, systemic illness (latrodectism), and, historically, death, though antivenom is now widely available.
Taxonomy and Classification
Red-backed Spiders belong to the Family Theridiidae (Cobweb Spiders). They are an invasive species in several countries outside Australia, spread via global shipping and trade.
Physical Description
Females are 10\text{ mm} long; males are tiny, 3-4\text{ mm} long.
- **Adult Female (Key ID):** Shiny, jet black, pea-shaped abdomen with a characteristic, prominent **red or orange stripe** on the upper side. She builds an irregular, messy, “cobweb” style web, often close to the ground.
- **Adult Male:** Small and harmless; usually brown or beige with faint white markings.
- **Bite ID:** The bite is often felt immediately as sharp pain, followed by localized sweating and increasing systemic symptoms.
- **Conflict:** Public Health (Venomous), Structural (Nesting Nuisance).
Distribution and Habitat
Native to Australia, but established in parts of New Zealand, Southeast Asia, and Japan. Habitat is sheltered, dry, and dark areas, often nesting in clutter, under rocks, garden furniture, eaves, sheds, and especially around domestic appliances or meters.
Behavior and Conflict
The conflict is the female’s nesting habits and potent venom.
- **Aggression:** Only the female bites, and usually only when her web or egg sac is disturbed.
- **Nesting:** They build their messy webs in areas frequently accessed by humans (sheds, mailboxes), increasing the risk of accidental contact.
Management and Prevention
Management is **Habitat Reduction and Exclusion**.
- Reducing clutter and debris around the house and yard (e.g., stacked pots, tires) where they prefer to nest.
- Application of residual insecticide dusts or sprays to the sheltered harborages where webs are found.
- Always wear gloves when cleaning dark, cluttered areas; seek immediate medical attention if bitten.
Conservation and Research
While generally controlled as a pest, research focuses on understanding the neurotoxins in their venom for pharmaceutical development and tracking their invasive spread globally.