They do darken in color when they prepare to pupate. When you say they are pretty small, how small do you mean? There is often a difference in sizes, but for the most part, they top out at about 3/4" long, however, every once in awhile I will have some 'hulking monsters' that are a about 7/8" long. I see you are in Pensacola Florida. You know that these are common throughout the entire southeastern U.S. and are quite easy to culture outdoors? As far as breeding them in a controlled enironment or 'captivity' so to speak, I think that it would be difficult, because from what I've read, they are required to mate in actual flight which would require a VERY LARGE cage or room of some type. I have 2 5-gallon buckets outside that have over 2,000 in each bucket (I actually meticulously counted out 1,000 and based on how many were left, I estimate 2,000 per bucket.). PM me if your interested in info on how I do it. There are a bunch of videos on YouTube as well on setting up buckets. It's very easy and very cheap.