Supposedly it’s your blood type.
I tested the wife no long ago as she had no idea what her type was. Turns out we are both O+.
Good theory though, but I still think some sort of body chemistry thing is at work. Mebbe all the rum I consume?
Nah, no booze in SEA and they ate me alive there. They would bite right through my utility trousers while I tried to sleep. Used to bundle up in a flak jacket and wear a gas mask to get some sleep. Beeeeeeeeeee........