Cwm Soden Nature Reserve in Pembrokeshire was teeming with insect life in the beautiful spring sunshine this morning, but it wasn't all as serene and peaceful as it looked. This lovely Early Bumble-bee (Bombus pratorum) has dozens of mites clinging to it's thorax. There's some debate about how much harm the mites do as they don't suck the bee's blood, simply using it to transport themselves around. However they obviously weigh it down and this one seemed very weak and was struggling to fly.
The poor noctuid caterpillar below is in a lot more trouble. Its been infected by a virus which has completely taken over its body and is even controlling its brain to change the way it behaves. Noctuid caterpillars are normally nocturnal, spending the day hidden deep in leaf litter, but this virus has made the caterpillar climb to the tip of a branch (or in this case bracken frond) on a hot sunny morning. The virus has been multiplying inside it for weeks making thousands of copies of itself which now burst through the caterpillar's skin skin as the green, swollen masses you see below.
The hot sunshine will dry the caterpillar out, killing it and releasing the viruses into the wind to infect another caterpillar and start the whole process over again.
This second shot was taken 30 minutes after I first watched the caterpillar climb up the bracken stalk. It is now dead and the masses of virues are already starting to turn black as they dry out.