The natural kind. One of the first rules of cruising is to never let cardboard on your boat. It is well known that cockroaches lay eggs in cardboard. In the past couple of days I have had a different twist. Flies. All of a sudden I have had a bunch of flies on Reboot. They were not healthy. That is they were easy to kill. I finally traced the source. At least I think I did. The boxes of kitty litter. When I opened one I discovered plastic bags of litter inside. Since then I have removed all of the litter from the boxes and the boxes from Reboot. No more flies.
Fair winds and following seas :)