The Littlest Horror

20 Sep

Latrodectus mactans‘ reputation proceeds it. The southern black widow is one of the few spiders in North America which can pose a serious threat to humans. It’s signature venom, latrotoxin, is a heavy neurotoxin that can induce spasms, uncontrollable crying, anxiety, heart rhythm irregularities. In rare cases it can also cause renal failure and shock. It’s cousins around the world carry the same danger within them.  As a child I remember long cautionary tales from my parents about checking for the signature cobwebs and swollen, marked abdomen. However, everything in turn has its nightmares. And if spiders dream, on dark nights they dream of this.

This horrific, obviously oh-so-dangerous creature is a dwarf scelionid wasp. This particular one goes by the name of Baeus. While the males are winged, the females lack any aerial capabilities and spend their life trundling around on the ground. All the better to find a black widow nest. Now, there is another kind of wasp that preys on black widows, the blue mud dauber. But Baeus is special because they don’t eat the spiders like the dauber does. Instead they go for the spider’s egg sacks, injecting them with their own eggs, parasitizing them. Baeus is what’s known as a parasitoid, like this guy, using their victims as living incubators for the next generation. Research by Cobb and Cobb showed that up to one out of every six spider’s nests fall victim to parasitoid wasps (although this fluctuates as the seasons change).

The black widow might be dangerous, but damn if this little guy isn’t just diabolical.

Sources:,, Wiki: Black Widow, Cobb and Cobb 2004.

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Posted by on September 20, 2011 in Natural History


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