http://en.wikipedia.org/wiki/Armadillidium_vulgare they are terrestrial crustaceans, but they have gills, i know this might be kind of a stupid topic but could it be practical and it be possible to select the bugs with better gills then the rest, have them breed with each other, so on and so fourth? i imagine if you take say 200 pill bugs, and put them under water, and wait until say 75% of them die, the other half is going to have better gills, assuming all are equally stressed out, and all the water is the same temperature after you take the 50 that are still alive you can breed them up too 200 really really easy again, because they have tons of little babies, and since it would be controlled a lot of them wouldn't die like out in the wild so the you do it over again, and over again and whatever! so then you eventually get this strain of pill bug, that has the ability to live under water how freaking neat that would be to make? and then you could start selecting them to have other ability's such as having colors, i imagine you can make some yellow because they often have yellow specks on there shells. the only real problems i see is breeding them to much they go retarded, so you might have to have several sources of them and then also a limit between being able to breath in water but not land, or visa versa but surely they evolved from the ocean so i guess they over come that. I kinda want to do it, perhaps they would be fairly valuable because they would make a great food source for water pets, like fish and salamanders but... i think theres already a species that is more or less a pill bug that lives in water, but i want to make my own haha Once you have these water living pill bugs, if possible you could bread them with water louse http://images.google.com/images?hl=en&q=Water+louse&um=1&sa=N&tab=wi and then they would be hybridized and so any interbreeding or recessive traits would vanish, because only dominate traits carry down with hybrids, or so i have heard. well... maybe it would be fun to try... i think i might the only loss i see is a few dead bugs and dirt under your nails haha Actually, im not to sure if they can breath at all under water, but perhaps i can raise the humidity so high that only the ones with more active gills can work? or perhaps get cold water and bubble a ton of air into it, making sure it doesn't have any CO2 if that was needed and then just keep them in there Why would it matter if they were underwater or not if there gills were covered in water anyways? surely there is a maximum oxygen concentration that can be dissolved in water, no matter what size the only thing that would matter is how much surface area it has right and of course its temperature since hot water has less oxygen but cold water has more If you could get them to breath under water they would still have there genetics telling them to live on land, so perhaps you would need to selectively breed the ones that don't crawl out and the ones that stay underwater?