Classic Black Widow Spider and Egg Sac, Order: Araneae, Family: Theridiidae, Genus: Latrodectus. This family of spiders contains 31 recognized species. Their common name was derived from observations where the male was devoured after mating, but this is not always the case. Not all black widows exhibit the red hour glass on the abdomen, some are white, yellow, brown or not all. Spots may be present. They are considered pests and have a dangerous reputation because they have unusually large venom glands which contain a neurotoxic venom, latroxin. The bites are rarely fatal. Their constructed webs are irregular, tangled and sticky which attracts all sorts of debris. They frequently hang upside down waiting passively for prey to become trapped in their web. Since they have poor eyesight like other orb weavers, they rely on web vibrations to signal trapped prey or a threat.