MONARCH REARING MAIN POINTS
You need to protect young caterpillars in a refuge cage. Believe me when I say, there is only one design that works: a mesh cage that can be unfolded and deployed in a matter of seconds.
DON’T rig up a do-it-yourself version of a cage: you will waste a lot of time, lose a lot of caterpillars, and expend much more effort than you needed to.The configuration that works is: milkweed plants, kept in their original pots, raised in fine-mesh-flexible-frame cages. Please just accept this advice, since it is the product of many hours of trial-and-error.
Do a search on these terms: mesh cage butterfly.
Some brand names for mesh cages are Restcloud, Qingo, Miraclekoo, Ueetek, Trasfit, Oxel, Petforu.
A cage of 36 inches is ideal.
When you see an newly-emerged adult fluttering around: open the cage door and let the butterfly go.
TACHNIDS DON’T FLY AT NIGHT
Only open the refuge cage at night, which is when tachnid flies are not active. If you open the refuge cage during the day, and a single tachnid fly gets into your refuge cage, it will kill all the caterpillars.
ANCHOR YOUR REFUGE CAGES
Use flat rocks or flat concrete stepping stones to weigh down your refuge cages. If you don’t, a gust of wind could blow the cage over, and the hanging chrysalises will be disrupted and die. Don’t clutter your refuge cage.
DONT GIVE TACHNID LARVA ANYPLACE TO HIDE
Tachnid larva growing inside a caterpiller will wait until the caterpillar turns into a ‘hanging J’. Then, the larva will burst out, slide down a thin thread, fall to the bottom of the refuge cage, then try to slide under a pot or dig into dirt. If the larva finds a place to hide in your refuge cage, it will emerge in a few days as a tachnid fly, and the fly will proceed to kill all your caterpillars. Keep the refuge cage uncluttered. A refuge cage should contain only one or two stepping stones to anchor it, and the pots which hold the milkweed plants.
DON’T BUY MILKWEED PLANTS THAT HAVE BEEN TREATED WITH INSECTICIDE
At the nursery, look for milkweeds that have caterpillars crawling around on them, and look for Monarch adults flying around. If you don’t see any caterpillars or adult butterflies, then assume that the milkweeds have been treated with insecticide. Don’t buy these contaminated milkweeds, no matter how good they look at the nursery.
EVERY STRING DANGLING FROM A DEAD CHRYSALIS MEANS THERE IS A TACHNID LARVA LOOSE IN YOUR REFUGE CAGE
If you see strings dangling from a chrysalis, take the chrysalis out of the refuge cage immediately and dispose of it somewhere away from your yard. Then, you need to find one larva for each and every string that you saw hanging from the dead chrysalis. You really shouldn’t have any difficulty distinguishing a tachnid larva from an early-stage caterpillar: the Monarch caterpillars have 2 cute little black antennas. The tachnid larve are slug-like and move like inchworms.