A man who thrives on the initial feeling of 'butterflies' generated by a new romance but who easily cools of the relationship once the feeling wears abates.
"Everything was going great for the first month and he was super into me but as soon as the initial 'butterflies' wore off he was gone."
"I dated Lepidopteromasculus guys one month at a time for two years! They are the worst."
I wonder if a lepidiopterist uses pictures of broad-winged insects on his visual-sharpness chart and asks you to identify which species they are, rather than just showing you one with all of those stupid/boring "E"s dat you merely need to discern which compass-direction they're pointing?