The Ladybug Mimic Spider (Paraplectana duodecimmaculata)
Ladybugs are brightly colored with what biologists call aposematic (“warning”) coloration: a warning to predators to avoid them because they’re bad tasting (ladybugs contain toxic and foul-tasting alkaloids). Such coloration is common: other examples include black-and-orange striped bees and wasps, the orange-and-black monarch butterfly, and the striking pattern of the noxious striped skunk.
Once an aposematic model species is in place, there is an advantage to tasty and nontoxic species to evolve the patterns and colors of the model, for by so doing they avoid predation. This form of imitation is called Batesian mimicry after the British naturalist H.W. Bates. In this way, potential predators of the non-toxic (when ingested) spider avoid it, as it has evolved to look like the toxic (when ingested) ladybug.