Friday, August 8, 2014

Spider Posing as an Ant

It’s interesting how many creatures have appearances and behavior patterns that cause them to mimic other species.  I love to find such creatures.  Many cause me to do the classic double-take as I dismiss them as something common and then snap my attention back because of some little thing that didn’t seem quite right.  This little fellow had me doing just that.  It’s part of a group of spiders considered ant mimics, meaning that many organisms mistakenly consider them to be ants.

Since I see these spiders fairly often, I assume them to be common at Blue Jay Barrens.  Their mimicry is less effective when they are at rest, but they are seldom still.  They move as a foraging ant moves, scurrying around the surface of plant leaves or chasing back and forth across a patch of bare ground.  When they do stop, they move their front legs in a manner similar to the movement of ant antennae. 

This is a Castianeira species and it does an excellent job of masquerading as a large black and red ant.  In most cases, animals will mimic a species with superior defensive capabilities.  It seems that both ants and spiders are equally equipped with weaponry suited to dissuade attackers.  Maybe the spider benefits by evading the notice of some predator that specifically seeks spiders.

Here’s the model for the mimicry.  When in motion, the spider is almost indistinguishable from Formica exsectoides, the Allegheny Mound Ant.  The Mound Ant is here in abundance and is to be found foraging on every stationary object in the landscape.  They are so plentiful that ant mimic spiders easily blend in as part of the throng.  It’s just a joy to observe an oddball ant and have it turn out to be an ant mimic spider.

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