redback

redback, (Latrodectus hasselti), species of black widow spider that is native to Australia, the females of which are venomous and distinguished by an orange or red stripe on the back of the abdomen.

Physical description

The body color of males and females typically is brownish or black, and both sexes have a reddish orange marking in the shape of an hourglass on the lower side of the abdomen. Males often have white markings on the upper side of the abdomen. They further differ in appearance from females in size, measuring about 3 to 4 mm (0.12 to 0.16 inch) in body length, compared with 10 mm (0.4 inch) in females. Males also are shorter-lived, surviving several months to the females’ two or three years.

During mating, the male somersaults into the fangs of the female, which in the majority of instances results in the female’s cannibalizing the male.

Britannica Quiz

Deadliest Animals Quiz

(Read Britannica’s list “6 Animals That Eat Their Mates.”)

Bite

Redback spiders typically live in dry sheltered spaces and may be found in areas in close proximity to humans, such as sheds and the undersides of play equipment. Bites can occur when a person makes contact with a female redback spider in her web. Humans bitten by female redbacks may experience strong, localized pain, swelling, and sweating. Systemic symptoms include nausea, vomiting, restlessness, and increased blood pressure; in severe cases, respiratory failure may occur. In many instances, severe reactions may be prevented through the administration of antivenom. A redback spider bite is rarely lethal.