Reading the photo's cation, "The sand flea Tunga penetrans, here in a scanning electron microscope several days after penetrating the skin. The abdominal opening protrudes on the right," I thought it was an image of the flea in situ with it's ass stuck through a chunk of the skin it was excised with.
In fact, that giant doughnut around it's midsection is the part that "over 2 weeks [...] swells up to many times its original size, reaching a diameter of up to 10 mm." It's not even fully distended in the photo. Fully inflated, the flea looks like a pearl onion. A fecund pearl onion under your skin erupting with eggs.
When Satan was going through puberty, these were his blackheads.