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Photo#1240618
Egg sac parasites?

Egg sac parasites?
Los Angeles, Los Angeles County, California, USA
June 17, 2016
Size: ~6mm sac; ~0.5mm larvae
Full size image

I've been observing some patio Uloborus with egg sacs lately, hoping to catch a hatching, and at one point noticed a tiny fly(?) on one of the sacs... Mom didn't seem to be taking much notice, and hadn't repaired the web that day, but didn't seem to be dead. Today I took a picture of a sac that had been on the wall for a while, not too close to any existing webs... what's going on in this picture? There appear to be some larvae, and a tiny orange arachnid is visible above the sac... and what looks like maybe unhatched Uloborus inside? Is there a parasite that preys on these?

Moved
Moved from ID Request.

Possibly chalcids...
There are a few chalcid parasitic wasps that are known to attack Uloborus egg sacs. You may want to keep an eye on this, or place the structure in a jar to see what develops, or what adults may eventually emerge.

 
Sure enough...
...I found this happening on a recent egg sac.

 
Interesting, thanks!
I'll keep an eye out.

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