anywhere humid and tropical is almost guaranteed to have scarlet millipedes (Trigoniulus corallinus), a successful invasive species thought to have originated in Southeast Asia.
more so than any of the other little millipedes I come across, these seem to be constantly copulating, even out in the open in daylight like this pair in Miami. in captivity, I’ve noticed T. corallinus males will attempt mating with any millipede they can catch, including male Narceus many times their size, who are typically unimpressed with their tiny suitor’s gentle, rolling tickles.
only a pair of the same species, though, can mate successfully, and this is for mechanical reasons: millipede genitalia are often shaped so that a male’s gonopods (modified legs used to deliver sperm) can only connect with a female of the same species. this makes the gonopods a vital source of identifying characteristics for diplopodologists!
curiously, the T. corallinus I found in Sarawak—closer, probably, to their point of origin—were a much darker, duller red. no less amorous, though
