Had a wonderful year raising monarch caterpillars (388 resulting butterflies tagged and released) along with 181 wild caught butterflies. Fewer than 1% of monarch tags ever get recovered and reported so we expect to learn what happened to maybe four or five. One has already been reported in North Carolina that is many hundreds of miles south of us i(where NY, VT & MA meet).
Some lessons learned:
1. Caterpillars have lots of enemies: sucking critters like stinkbugs and spiders; Raising them inside behind a bright window boosts their rate of survival.
2. Feed caterpillars sprigs of fresh milkweed every day but wedge in flexible foam above water to keep leaves vibrant (otherwise caterpillars can sink and drown);
3. Periodically harvest a quarter of outdoor milkweed patches to promote new growth: all but a few of our caterpillars originated on plants less than three weeks old. Thousand of older milkweeds never had a caterpillar!
4. Chrysalises must hang from a horizontal surface: emerging butterflies can't develop flat wings unless they can hang them straight down as they harden. Glue loose chrysalises to toothpicks and suspend them from a wood "tree" (use wood glue: hot melt glue will cook them)
5. If they are not ready to fly, release butterflies on the leeward side of the trunk of a tree or other stable surface. Breezes may make them fall if placed on swinging branches or flexible plants.
6. Tags for the underside of a rear wing may be purchased from: https://monarchwatch.org/
and this organization will keep you informed of reported sightings of those you tag. They also have lots of information on Monarchs and their food.