I'm failing to see whatever it is you see, though I clicked through to the full size picture before looking at the thumbnail, so my view of the thumbnail was influenced by having seen the full size picture
I don't have thumbnails set on my phone so I only ever saw the full image. That said, I looked at it without my glasses with my arm outstretched and I'm going to guess they saw either buttcrack or titcleft
Increased surface area. Only male glowworms metamorphose into adult forms and they use their feathery antennae to track females down by their pheromones. Increased antenna surface area helps them pick up those pheromones.