(Mycodiplosis)

(Mycodiplosis)

Observation - (Mycodiplosis) - UK and Ireland. Description: At first I thought that this was a fruiting body of the rust but closer inspection showed it to be an invertebrate of some kind. A single birch leaf (Paperbark Birch (Betula papyrifera), I think) had 32 of them, perhaps feeding on the rust (possibly Birch

At first I thought that this was a fruiting body of the rust but closer inspection showed it to be an invertebrate of some kind. A single birch leaf (Paperbark Birch (Betula papyrifera), I think) had 32 of them, perhaps feeding on the rust (possibly Birch Rust (Melampsoridium betulinum). The photo shows a big one, perhaps 2mm long. Can anyone help with an ID, please?
Edit: Title changed to match agreed ID.