Summary: Every so often, there are bugs. Luffy the Entomologist.
Notes: Anonymous on the OP_fanforall meme asked for "Entomologist Luffy". Quite some time back, actually, like OMG over 3 years. Re-reading it prompted a snap decision to post.
Disclaimer: Not mine, no profit, yadda, yadda, yadda.
Every so often, there are bugs.
Normally, this follows a less eventful stop on a quieter island - one that didn't end with them fleeing from the local marine forces, townsfolk with pitchforks, or irate wildlife. One where they had opportunity to relax, shop, explore the island and enjoy the simple act of walking over dry land with green grass beneath their feet.
On such occasions, the nets and jars come out. Luffy, almost unprecedented any other time, is seem dusting off books. Not just thin pamphlets, but heavy reference tomes that give Robin pause. With backpack and shoulders overloaded with equipment, he cheerfully sketches what barely qualifies as a wave behind him, and the last they see of him for two or three days is his dwindling back.
Sometimes Usopp has gone with him, and once or twice Zoro, Robin, Chopper... but never more than one other. For the most part, when they have such a chance to stop, everyone has their own thing to do.
And this is Luffy's.
When it's time to leave, he brings his prizes back to the ship, most still crawling. For the next few days, Nami exiles herself to the crow's nest and Sanji locks himself in the kitchen, and they stop sleeping on a night until their eyes are ringed by dark patches. Then Luffy finally notices that some of his nakama are not greatly endeared by his hobby, and the living specimens become lifeless exhibits pinned to card.
Inevitably, Nami feels bad because they had pet names, and he talked to them, and how could he? But it's Luffy, after all. Why should any of them be surprised that his hobby is morbid as well as creepy?
The cards and their hard little corpses are consigned to wooden trays that Usopp made, stacked and wrapped in oil cloth in one corner of the mens' cabin, and mostly ignored except by Sanji, who still takes a wide diversion around them, until the next such island stop.
Four hundred and sixty-seven different specimens of Coleoptera so far.
There'd be more, since after all there are hundreds of thousands of beetle species - so Luffy tells - to collect, but he's had to re-start seven times from scratch due to flood, fire, or other loss.
And, occasionally, he eats them.