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Fall Fund Drive

aphid with yellow ball - Uroleucon eupatoricolens

aphid with yellow ball - Uroleucon eupatoricolens
lancaster County, Pennsylvania, USA
June 29, 2009
Can you please tell me about the yellow ball on the aphid? What is it and why does the aphid hold it extended as pictured?

Moved from Aphids. ID (Uroleucon eupatoricolens) based on host plant, which looks like Eupatorium maculatum. I suspect the defensive secretion is released in response to being harassed by a predator, as you suggested.

Cornicle secretion.
It's a defensive fluid that would gum the mouthparts of predators when they would try to eat it

Very interesting! Is the fluid produced in response to an immediate threat from a predator? I notice none of the other aphids have it and I wonder why.

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