Wildlife Spotting

When I first saw this, I thought it was a small fungus growing on a tree's bark. Looking closer, I noticed that it moved. I took some photos, but when I leaned on the tree for a better position, it fell to the ground, and disappeared into the grass. At first, it seemed that it was a ichneumon parasitized insect but, looking better, I noticed that the yellow bulges in its body were not as even as they would be if they were larva cocoons. I suspect that this poor guy is infected by some sort of fungus.