I haven't observed breeding behaviors when I release a large group of Monarchs. However, if there is a male in my yard that I didn't raise, he will move in as soon as a female is released and knock her down, and "knock her up" immediately! So I wouldn't worry too much about interbreeding. Even when I keep a group of Monarchs together for several days before releasing them, I never get any mating behaviors. They may be programmed to seek out unrelated mates. Been doing this for 30+ years, and that's been my experience. Now, just as soon as I write this, you will have siblings attempting to mate.

I've been raising caterpillars for about ?12 years, and I've never seen siblings mate in the cage before release, even with gulf frits, who will wait for a female to emerge from her chrysalis and mate with her before she's even dry!
Also, I don't know anything about butterfly genetics, well, I learned that it's the females that carry the differing sex chromosomes - like the human XY - and males carry two of the same - like human XX. But their genetic makeup is PROBABLY too simple for it to matter, don't know for sure.

Sherry

I've never seen mating occur within my rearing tents, and I have also raised lots of Gulf Frits. I wonder if it does matter though. We need a scientist's opinion. :o)

Monarch Lab (University of Minnesota) says "Inbreeding can cause fitness problems and deformities."

Didn't have to worry about that with the female Queen I raised...and then released this week. Now, I did worry about whether it could even find a mate!

Thanks for all the replies. I plan to release these immediately. So, hopefully they can all find an appropriate mate.

Martha