What's That Bug? does not endorse extermination

Subject: Spiderlings…hatching? Or a communal web???
Location: Montrose, CO
June 16, 2016 10:58 pm
Dear Bugman,
I’m a longtime fan of the site, though I haven’t had much cause to send any id requests in between your wonderful archives and my trusty field guide. But this one was both interesting and perplexing: while visiting family in western Colorado, I walked out the front door and spotted what looked like a lot of large grains of sand caught on a small three-dimensional web spreading from the front step to the post of the railing (perhaps 10 cm long and the same height). When I looked closer, I saw that the “grains” were hundreds of little yellow balls about 1-2 mm in diameter, stuck all over the cobweb structure, with here and there a few very tiny yellow spiders moving around. In the 30 seconds it took to get my camera, ALL of the “grains” had turned to the same spiders–hundreds of them!
The only explanation I can think of is that the balls were eggs and the spiders were hatching from them en masse (though they had all hatched by the time I got the camera), but I’ve never heard of a spider laying eggs all over a web like that rather than making an egg sac. Any ideas?
Signature: Susan

Orbweaver Hatchlings

Orbweaver Hatchlings

Dear Susan,
We believe these are hatchling Orbweaver Spiderlings, and that they have just emerged from a traditional egg sac like you have described.  Even immediately upon hatching, Spiderlings are able to spin silk, so what you witnessed can be described as a communal web, though not a web in the traditional sense.  Orbweavers disperse using a technique known as Ballooning.  The spiderling releases a strand of silk that catches the wind and transports the individual to a new location far from its siblings that would compete for food as well as pose the potential threat of cannibalism.  We believe the Spiderlings in your image are just waiting to catch the breeze.

Orbweaver Hatchlings

Orbweaver Hatchlings

What's That Bug? does not endorse extermination
Location: Montrose, Colorado

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