Spider Milk Mystery

Can spiders milk each other?

I didn’t think so, but I recently saw two spiders doing something so bizzare that I’m not sure what else to call it. I was hiking in a forest south of Bozeman, Montana when I noticed two spiders interacting on a web. I stopped to watch them and saw this:

If you’re as confused by this as I was, let me walk you through it. The spider on top would drum the bottom spider’s abdomen with his pedipalps, then seemingly grasp a protruding gland on the bottom spider’s abdomen. After a couple of seconds, a strange orange blob would swell from the bottom spider’s gland and into the top spider’s pedipalp. This blob would then disappear into his pedipalp and he would snap his pedipalp up to his mouth, as if drinking the orange stuff. He would then repeat this process over and over, alternating between his left and right pedipalps. To my amazement, when I returned three hours later, the spiders were STILL doing this!

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Click twice for a closeup look at the two stages of this incredibly weird behavior. “Milking” on the left, “drinking” on the right.

I have absolutely NO idea what the heck is going on here. First of all, what is that orange goop? Second, how could the bottom spider possibly secrete drops of it for three hours without being sucked dry? Third, what is the purpose of the drumming ritual? Fourth, what the heck is going on??? If you have answers to any of these questions, please let me know!

I hope this story reminds readers that there are incredible things happening all around us in nature. During your hikes, try taking some time to just sit and discover them. When you notice the little things, it’s hard to be disappointed.

Update: The mystery has been solved! Click here for the answer!

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A crab spider waits with arms outstretched for unsuspecting prey. This critter was hunting just a foot away from the milking spiders.
Categories Field Notes, Invertebrates, MontanaTags

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