Latrodectus, mactans

Arthropods can be traced back over 560 million years ago. These arthropods were called chelicerates. Some of these arthropods were larger than humans, the Pterygotus was over 7 feet long. 440 million years ago sea scorpions moved to land and were the first land arthropods and perhaps the first land animal. 285 million, or more, years ago more arthropods made the move to land in the form of spiders.

Pterygotus 400 million years ago	Palaeophonus 400+ million years ago
Arthrolycosa 285 million years ago