Root pest weed.

Pulled up some fat hen, noticing it appeared slightly stunted. The root was rather deformed, with a roughly textured surface in parts, and there were some sort of insects on it possibly tended to by (red) ants, so maybe a hint there. Thickly clustered when pulled up, some dropped off before I coupld photographg them (would a full-res pic uploaded somewhere be useful?).

What are they?

 

Well, "root aphids" seems to be the answer, having consulted a knowledgeable person. I have been lucky enough never to have knowingly seen these before.

I don't suppose for a second that they'll attack "just weeds". I wish something would.

 

Root aphids feed on different types of plants, damaging the health of the source. Many aphids thrive in the stems and leaves, but the root aphid is different. This insect is found under the surface of the soil. Root aphids attack the plant’s root system, often killing the plant if not identified soon enough. Adult root aphid with nymphs.
How to Kill Root Aphids Naturally | Trifecta Natural
www.trifectanatural.com/problem