Dark-skinned caterpillars are stressed.
Most often, a dark-skinned caterpillar has tachnid larva growing within it.
Sometimes, a dark-skinned caterpillar is simply dehydrated
Tachnid fly timetable:
Tachnid flies start appearing mid-April
Tachnid flies come out at about 9:30AM
They seem to appear as the morning first warms up
They are less active in the heat of the day.
They reappear in the evening.
Tachnid fly swatting:
If you see a squirming caterpillar,or, one that fell and is squirming:
Beware: there is a tachnid fly in the vicinity.
Try to kill it: wait a few minutes with a fly-swatter handy.
Tachnid fly appearance:
a little smaller than a housefly
slower than a housefly
Cover some of your milkweeds when Monarch females are laying eggs:
If you don’t, the caterpillar population will suddenly explode, caterpillars will eat all your milkweeds, and some will starve.
Monarchs don’t tolerate heat over 90F.
Use sunscreen cloth to fashion a cover over your mesh cages
Shopping for milkweed:
If there are no monarchs flying around and no caterpillars crawling on the leaves,
don’t buy the milkweed, no matter how good it looks.
If you need to pick up a butterfly:
Put your index finger lengthwise in its path, NOT across its path.
The Monarch will crawl onto your nail and then onto your finger.
You can cup your other hand behind the Monarch to protect the wings.
Rinsing them off your milkweed with some solution or the other is an exercise in futility.
Partially control aphids by regularly trimming back your milkweeds, but this method is time-consuming.
You must quarantine any new milkweeds before introducing them to your sanctuary.