Head to head
Black Widow Spider vs Redback Spider
The black widow and the redback are the same kind of spider. Both are widows, in the genus Latrodectus, both are small, glossy, jet-black spiders with a red mark and a messy, sticky web, and the redback was for a long time treated as a subspecies of a black widow. The main difference is which side of the world you meet one.
| Black Widow Spider | Redback Spider | |
|---|---|---|
| Group | True widow spider (Latrodectus) | True widow spider (Latrodectus) |
| Where it lives | The Americas, mainly the warmer US and Latin America | Australia; introduced to New Zealand, Japan, and elsewhere |
| Top of the abdomen | Usually plain glossy black | Usually a bright red or orange stripe |
| Underside | A red hourglass | A red hourglass or blotch |
| Female body size | About 10 mm | About 10 mm |
| Male | Tiny, brown, rarely bites | Tiny, brown, rarely bites; often eaten during mating |
| Venom | Alpha-latrotoxin, a neurotoxin | Alpha-latrotoxin, a neurotoxin |
| Bite effect | Latrodectism: pain, cramps, sweating, high blood pressure, for hours to days | The same syndrome, effectively identical |
| Deaths | Extremely rare with modern care | Extremely rare; none clearly confirmed in Australia in decades |
Black Widow vs Redback Spider: common questions
Are the black widow and the redback the same spider?
Not the same species, but the same genus and very close relatives. They are both widow spiders in Latrodectus, and the redback was for a long time classified as a subspecies of the western black widow. Their body form, web, venom, and bite symptoms are all but identical. The clearest visible difference is the redback's stripe on top of the abdomen, which most black widows lack.
Which one is more dangerous?
They are about equally dangerous, which is to say serious but very rarely fatal. Both deliver a neurotoxin that causes latrodectism, a syndrome of spreading pain, muscle cramps, sweating, and raised blood pressure that can last for days. Effective antivenom exists for both, deaths are now extremely rare, and the people most at risk are young children, the elderly, and anyone with a severe reaction.
How do I tell them apart?
Location first. A widow spider in North or South America is a black widow; one in Australia is a redback. Up close, a female redback almost always has a bold red or orange stripe running along the top of its rounded abdomen, whereas most black widows are plain glossy black on top and show their red only as an hourglass on the underside.