Recently I gave my Why Natives? PowerPoint presentation to a local birding group which meets at Heckrodt Wetland Reserve. One of the questions asked at the end of the presentation was whether or not it was appropriate to raise monarch caterpillars at home — the questioner had heard pros and cons about this and he wanted to know what I thought.
I responded that “I didn’t think it was a good idea to do so unless one has the ability to check for OE.”

Deliberately spreading OE (Ophryocystis elektroscirrha) to other monarchs by raising them in captivity is counter-productive and downright diabolical, in my opinion. Having said that, rearing relatively small numbers of monarchs is a good way to learn about the butterfly’s life cycle and to contribute to citizen science efforts, but it’s important to be very careful in the rearing methods you use. Read about MLMP’s monarch rearing program.
For this very reason — disease — rearing monarch butterflies on a large scale as in “mass production” and typically in crowded enclosures should be frowned upon as more of a disservice than an enhancement of the monarch population. Here is what MLMP has to say about large scale captive breeding. I thought you might also like to read it’s accompanying position statement signed by a number of noted scientists and monarch experts.
If you feel you must raise monarchs, please keep records and report your findings to citizen science programs such as the Monarch Larva Monitoring Project (MLMP) and Monarch Health. And, by all means, learn how to detect OE.
All it takes to detect oe is a microscope capable of 100-400x magnification.. Digital microscopes or inexpensive light microscopes can be had for about $60 or less. My old student microscope from waaaaay back was quite adequate. Considering the probable costs of your other hobbies, this should be affordable.
Excellent information, Sarah. Thanks!