Hey! So fall is coming and I want to try to raise some wooly bear caterpillars (Isabella tiger moths) but I don't know how! Got any info?
Keep caterpillars in a plastic container. Airtight is fine as long as you open the lid for fresh air a couple of times a day (and it lets some excess moisture out). Pyrrharctia isabella is known to be occasionally cannibalistic*, so bear that in mind if you plan on rearing multiple caterpillars together.
Clean out frass (droppings) and replace food every day. Mop up excess moisture with tissue paper to prevent infection. Change or wash up containers every week or so, or more frequently if needed to avoid fungal/mould growth.
Isabella tiger moth caterpillars are polyphagous (generalist feeders) and feed on a wide variety of plants, including common weeds such as clover, dandelion and nettle. You can Google any others. I recommend foraging wild plants as they have less chance of pesticides.
P. isabella overwinters in the larval stage from autumn when it enters a fasting, wandering period, looking for a place to hibernate. This diapause, or hibernation period, lasts until the end of spring the following year, so you will need to accommodate this. I have no experience with Isabella tiger moths firsthand, but here is some advice from someone that apparently does:
“Dormancy can be induced in larvae by chilling them and keeping them cool. Larvae have been known to survive an entire winter completely frozen in an ice cube.** Warmth stimulates them, and in an active state they require food.
As long as the caterpilar is kept cold, it will remain dormant. I recommend putting the caterpilar in a small tupperware type container, lid on tight, no air holes or food. Mark the container and then put it in the refrigerator crisper where temps will be cold enough to keep larva dormant for the winter until food is available again in the spring. In the spring, as long as the rearing jar/container is kept clean and fresh foliage is supplied, the caterpillar will grow, spin its cocoon and then emerge as a moth.
If the caterpillar is warmed, it will need food or it will starve after a few days. If you have inadvertently warmed an hibernating larva, the caterpillar can be rechilled and put back into cold storage until spring warmth brings fresh foliage.”
You can probably keep them in a cage or a ventilated box as well, but you would have to mist them semi-regularly so they don’t dry out as the moisture evaporates from the air. And as already stated, chilling is a must. No food either; as already stated, the caterpillar won’t eat it.
I recommend removing the caterpillars from cooling around March. The flight period is from April to September, so this gives them a chance to fatten back up, rehydrate, cocoon, and emerge. Once cocooned, keep the cocoon well-ventilated and mist or wet the cocoon every week or so so it can’t dry out. It should have multiple sticks and things to climb and dry its wings out on upon eclosure, and plenty of space.
And I think that’s it!
* - Cannibalism has multiple causes in caterpillars beyond simple hunger, from chance opportunism to viral infection to competition reduction to the species just being plain omnivorous. I’m not sure which of these applies to P. isabella so I can’t advise you on how to reduce the chances of it happening beyond just keeping them apart.
** - Despite this, please don’t actually freeze your caterpillar in an ice cube.
The above is the larva of the death’s-head hawkmouth. The larvae are stout, reaching 120–130 mm, with a prominent tail horn. All three species have three larval color forms: typically, green, brown, and yellow. Larvae do not move much, and will click their mandibles or even bite if threatened. When mature, they burrow underground and excavate a small chamber where they pupate. (Source)