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Purple Infestation

Purple Infestation
Poulsbo, Kitsap County, Washington, USA
December 24, 2009
Size: Small - but billions


Hypogastrura (generally bluish, like in this picture) and Ceratophysella (generally more purplish) are known to form such spectacular mass aggregations.

Great shot!

Apparently they can freeze and it doesn't harm them? But why are they all around the foundation and they haven't disappeared by now - 4 days later? This image is only one area. I put an earthworm on top of them and they absorbed it.... it didn't crawl away, and it was gone within an hour.

Dear Mike
Many Collembola have a kind of anti-freeze protein in their blood. This will allow them to continue to be active at low temperatures when most other arthropods cannot move their limbs anymore.
Mass aggregations in Hypogastruridae have a purpose: replication. When a female got 'pregnant' she will leave the aggregation to lay eggs. Depending on the size of the aggregation it will take a few days up to a few weeks for the aggregation to disappear.
Collembola do not feed on earthworms. The worm disappeared probably because it was simply covered by the Collembola specimens.

Moved from ID Request.

I'm uncertain whether the springtails in this image can be reliably identified further without close-up images, but I thought the documentation of their mass aggregation was neat enough to include in the guide.

Possibly something in Hypogastrura?

Must be springtails
An individual springtail looks like this:

You can read about them here.

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