This caterpillar was alive not sure what was attatched.
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Just a guess - the attachments could be eggs from one of the many species that parasitise caterpillars. Not sure what though!
I doubt very much they are eggs, just too big. I think these are emerging parasitiod larve, almost certainly from some sort of hymenopterous species. If you look carefully there appear to be more emerging underthe body of the caterpillar as well.
If you look at the photo at maximim resolution you can see what appear to be strands of silk running from the leaf to the body of the caterpillar in the area where the larvae are. I think this is the start of the coccoon for these parasitoid larvae.
Tachinid Recording Scheme
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Fascinating but grisly!
Lat/Lng: 51.2367, 1.0225
OS grid ref: TR110529