Wikipedia
Micrathena
The spider genus Micrathena contains more than a hundred species, most of them Neotropical woodland orb-weavers.
Only three species occur in the eastern United States: females of M. gracilis (the Spined Micrathena) have five pairs of conical tubercles on the abdomen, female M. mitrata have two short posterior pairs, and female M. sagittata (the Arrow-shaped Micrathena) have three pairs.