Monarch Watch's focus is Eastern population; the group of monarchs that breed in states east of the Rocky Mountains in summer and migrate to central Mexico annually in the fall.

• We only ship larvae to areas within the United States, east of the continental divide due to USDA federal regulations. 
  • Montana prohibits live monarchs to be shipped anywhere in the state.
  • Connecticut no longer allows the release of butterflies with the exception of Educational institutions, Zoos, Nature Centers, and similar organizations.

The group of monarchs, cleverly dubbed the Western population, breed west of the Rocky Mountains and migrate to southern California (one of the major overwintering sites is Pacific Grove, CA) annually. The consensus among Monarch biologists (although the topic is still debated in certain circles) is that the two populations are genetically distinct. That is, they aren't known to interbreed. For information on tagging and rearing monarchs west of the Rockies please contact The Xerces Society or Monarch Alert.