the enemies of a western black widow
In a window well of an old house, a black widow has created a luxurious home. Dead husbands and other insect corpses hang in the silk threads, a testament to her deadly nature.
A clear plastic lid protects her home from weather, but a recent hail storm cracked it, leaving her vulnerable.
She spends long hours guarding her egg sack. Who could possibly threaten her in this out-of-the-way home?
A very small wasp (photo), Philolema latrodecti, lays eggs inside her victims. The wasp larvae feed on the spider from within until they burst out, fully grown. P. latrodecti and a similar, even smaller species, Baeus latrodecti live in the American south, among southern black widows.1
The widow spider genus is Lactrodectus, hence the parasitoid wasps named latrodecti. There are unique widow spider species on five continents. In North America we have:
Lactrodectus mactans, southern black widow
L. hesperus, western black widow
L. variolus, northern black widow
(invasive) L. geometricus, brown widow, native to Africa
In the western black widow range there is a blue mud wasp, Chalybien californicum. (photo)
The blue mud wasp is kind of a bad ass. It steals the nests of black and yellow mud daubers. It removes their larvae along with any dead and dying spiders, caterpillars, etc. that they were feeding on. The blue mud wasp brings in a fresh kill for it’s brood. Often its prey is not killed, but is sedated or zombified to the point that it doesn’t move enough to escape while being eaten.
Sounds hellish, but the good news is it’s not an aggressive stinger of people. Let them do their evil and keep the spider population in check.
Another foe of the widow spider is the praying mantis. It is the judo master with precision movement and timing. It grapples with it’s giant spiky forelimbs, and disassembles an opponent with it’s mandibles.
A praying mantis can absorb bites from many spiders. It may experience temporary paralysis, while maintaining a vise grip on its meal, which it resumes eating after the venom wears off. However, the widow’s neurotoxic venom is especially strong, and serves as a powerful deterrent.2
Most birds, reptiles, and small mammals avoid these spiders. One exception is the shrike, a.k.a. the “butcherbird”, known for impaling prey on plant spines and other thorn-like fixtures. It’s a violent, clever maneuver that neutralizes the threat of a bite to the face, feet, or inside of the mouth. There are two Shrikes that spend time in the western black widow’s range, the Northern Shrike3 and the Loggerhead Shrike4.
Widow spiders hide and avoid. But I’ve noticed when the spider at my house has an egg sack, if I come close, she scuttles around almost as if to make her presence known before retreating to guard the sack. It feels kind of like a threat display.
If she were to bite me, there would be a 15% chance of a ‘dry bite’ in which envenomation does not occur.5
This proud black mother is nearing the end of her life cycle. She dies when her children kill her. The brood expands to neighboring enclaves. The males stick around long enough to mate and are killed.
A guy walks up to the widow at her husbands funeral and says, “May I just say one word?”. “Sure” she replies. “Plethora”. The widow says, “Thanks. That means a lot.”.
Philolema latrodecti https://entnemdept.ufl.edu/creatures/beneficial/wasps/latrodectus_parasitoids.htm
America’s Poison Centers’ annual report tracked about 3,500 spider bites in the U.S. in 2021, with about 40 "major" clinical outcomes. Nine of those serious outcomes were attributed to black widows; 29 major outcomes and the only death that year were attributed to brown recluses. There were no spider bite deaths in AAPCC's 2020 report, which tracked seven "major" black widow bites and 23 "major" brown recluse bites.
Norther Shrike https://www.allaboutbirds.org/guide/Northern_Shrike/id
Loggerhead Shrike https://www.audubon.org/field-guide/bird/loggerhead-shrike