This is a tiny larva of one of the Green Lacewings (Chrysopa sp.), one of the fiercest predators of aphids and other small plant-feeding insects. It has the decidedly odd habit of covering itself with the remains of its aphid meals. It is said that this helps to camouflage it and enables it to creep up on aphids undetected...but I'm not convinced. If I was a tiny aphid I think I might notice a stinking heap of animal remains coming towards me! I think it might help it hide from predation itself, by birds in particular. However, even this is not very convincing as the pile of detritus it drags around tends to make it stand out more on leaves. In my view, it is just a wierd, fetishistic killer that has escaped from a Nordic noir drama.