The distinctively colored male Ladybird Spider (Eresus cinnaberinus) may grow to 11 mm, much smaller than the females. This species, which may actually be 3 species, is found across Europe, but known to be most common in Central and Southern Europe. The coloration may be mimicking ladybird beetles (family Coccinellidae), which are mildly toxic and distasteful to predators.
A small and colorful male Ladybird Spider (Eresus cinnaberinus) slides under the much larger female for a precarious mating maneuver. The males grow to 11 mm, while the females are up to 20 mm in length. This species is found across Europe, though some scientists break up the 3 races of this spider into 3 species.
Paxon Identifies Your Motherfucking Spiders (pt. 82):
female Ladybird Spider (Eresus moravicus), from central and eastern Europe. while the males of Ladybird Spiders (Eresus spp.) are smaller and brightly colored (red and black like ladybird beetles), the females are robust and more darkly colored, sometimes with yellow on the face.