The green heart spider (Gnolus cordiformis) is a little inhabitant of temperate woodlands in Chile and Argentina. The name cordiformis comes from the Latin and means “heart-shaped” — an obvious reference to the shape of their abdomen (the spider “bum”).

The green heart spider, Gnolus cordiformis.

Gnolus is in the orb weaver family (Araneidae), but it does not spin orb webs — in fact, it does not spin a hunting web at all! These spiders have abandoned the web-building habits of their ancestors and now hunt their prey by ambushing them in the vegetation with their legs armed with strong spines.

The orb web that typical orb weavers spin — but not Gnolus!

Because Gnolus no longer builds orb-webs and hunts with its spine legs, it was once classified in the same family as pirate spiders (Mimetidae), which have similar hunting habits. It was not until 2012 that DNA sequences showed that Gnolus is actually more closely related to araneid orb weavers. Other examples of spiders who abandoned their webs to ambush their prey in the vegetation include the Australian triangular spider (Arkys cornutus) and some long-jawed spiders from Hawaii (Tetragnatha) — all of which have independently reached the same general morphology, with strong legs armed with spines for capturing their prey.