Arrow-shaped Micrathena Spider

These striking spiders look like they ought to be related to the spiny orb-weaver (Gasteracantha sp). They are in the same family (Araneidae) but a different genus (Micrathena). They have fewer spines than Gasteracantha (and, again, probably a bunch of smaller details, like the number of hairs on the thorax or which way some microscopic…