A Very Special Spider

While walking in Julie Metz Wetlands earlier this week, I spotted a brown mass on a leaf.  It looked like a large bird dropping, and I thought it could also be a half eaten frog or toad.  I whipped out my trusty camera with macro lens and took a picture.

To my surprise, it was a very special spider called the Bolas Spider, in the genus Mastophora.  Bolas Spiders are so named because they capture their prey by using a sticky blob of silk called a bola on the end of a silk thread.  In the non-spider world, a bola is a weight on the end of a rope, used by South American cowboys as a sort of lasso.  The cowboy entangles the cow’s legs with the rope and weight, stopping the cow from running away.

The Bolas Spider creates her bola, and also secretes a pheromone of a particular moth species to attract a moth.  When the moth approaches, the spider cocks her leg and swings the bola.  If the bola hits the moth, the moth sticks to it, the spider reels in the bola and the moth, and wraps the moth up in silk webbing for her later dining pleasure.  She typically catches two moths a night, but will sling her bola at any insect that comes close.  In the unlikely event that she doesn’t catch anything, she will consume the bola.  There is an interesting video on You Tube that shows her technique. http://www.youtube.com/watch?v=2UfMJJAzvbI

Males are much smaller, and don’t use bolas to catch prey.  They perch on leaves and grab prey with their front legs, much like many crab spiders.  Male Bolas Spiders are unique in their own way, as they are sexually mature from the moment they hatch, very unusual for spiders.

I mentioned earlier that I had originally thought that the brown mass was a bird dropping.  This defensive coloration allows the spider to rest in plain sight, as most animals that eat spiders ignore bird droppings.  All in all, this is a very special spider.

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2 comments so far

  1. Ernie Sears on

    A great defensive strategy – very cool! Nice catch.

  2. Kim Hosen on

    You have been seeing some very cool critters at Metz Wetland… I’m going to have to visit soon!


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