White Micrathena Micrathena mitrata

Despite its fearsome appearance with a shiny black abdomen and spiky yellowish-brown legs, this tiny spider is completely harmless to humans. Females range from 4 to 9 millimeters long while males are even smaller at just 3 to 4 millimeters, yet they manage to construct elaborate webs to catch insects. There's dramatic sexual dimorphism here—females are significantly larger than males, a pattern common in many spider species. Found across a wide range from the United States through Central America to Brazil, this little spider is a perfect example of how looks can be deceiving: it appears formidable but poses no threat to anything larger than its insect prey.