I've chronicled my previous experiences with a millipede species that fluoresces under ultraviolet light previously here and here, so if you want a primer about Semionellus placidus, check out those posts. I've established that this species fluoresces under UV light quite nicely, and I've found it in the field from spring until fall. It also appears to be quite abundant (in southeastern Ohio, at least) and lights up the leaf litter whenever I'm looking for it.
UV fluorescence in arthropods isn't anything new: it's been reported most notably in scorpions, many insects, and some other millipede species. A few months ago, however, I found something new: UV fluorescence in the eggs of Semionellus placidus. I haven't found other mentions of this, and the literature I've read has shown the fluorescence in post-egg stages, chalking it up to chemicals in the exoskeleton.
Needless to say, this is pretty neat. I'm currently keeping some of the eggs in a separate container, hopefully to hatch them out. I'm not sure how that will turn out, however, as I recently checked on them and it looked like a fungus got to them.Under normal light, the eggs don't look like anything special, as you can see below.
Now, time to investigate this further...