Western Black Widow (Latrodectus Hesperus) — This juvenile female black widow is certainly beautiful …but take that red hourglass marking on her underside as a warning. While they are not aggressive (will not attack you), they will defend themselves or their egg sacs if you mistakenly grab or step on them. They have incredibly strong venom and a painful bite. Symptoms include: pain in the chest / abdomen, muscle cramping and spasms, difficulty breathing, nausea, chills, a severe increase in blood pressure, and more. A beautiful spider that is best left alone. Photo by Glenn Marangelo on 6/3/17 in Missoula, MT.