The scientific name of a Black Widow is Latrodectus and is a genus of spiders in the family Theridiidae.
This spider can often be identified by its dark-colored and reddish hourglass-shaped markings on the abdomen. [Source: Wikipedia]
Black Widows have a venomous bite because of the neurotoxin latrotoxin which causes pain, muscle rigidity, vomiting and sweating.
Only female bites are dangerous to humans and they are very rarely fatal to humans.
So can bearded dragons eat black widows?
No, they cannot eat them at all.
This spider is extremely dangerous for a bearded dragon and therefore should be fully avoided.
Do not let your bearded dragon near this spider as they are poisonous and could possibly kill your lizard.