Saturday, June 6, 2015

Raising Wild Silkmoths: Pt. 2

Look who hatched today!

These are newborn Cecropias from those eggs I gathered 11 days ago.

Aren't they cute?

So they've just been born - now what?

Their first order of business is to eat the shell they hatched from - it contains protein that helps give them a head start.

Newly hatched Io Moth caterpillars
Soon after they'll be wandering in search of leaves to eat. But what leaves?

For Cecropias, Black Cherry (Prunus serotina) is usually their food of choice, but this may vary depending on where you live. They are also known to feed on Box Elder (Acer negundo), Sugar Maple (Acer saccharinum) Alder and Birch (Betulaceae).

If you aren't sure which of these they will prefer, go out and see which tree is the most prevalent in your locale. If you find all tree species listed as potential food plants for your moth species, just collect a sample of each and see which they decide to feed on. However, it's important to not suddenly change tree species after they've begun to feed on one.

When they are this tiny, I find it's easiest to keep up with them in a Zip-lock bag or some type of Tupperware container. You need something that will hold moisture and keep the leaves fresh, as well as keeping these tiny boogers from wandering off.

Now comes the fun part: watching them grow!

Caterpillars have the fastest growth rate of anything in the animal kingdom, save bacteria and viruses.

They will increase their size by at least 1,000 times before reaching the pupal stage.

A Cecropia nearing the pupal stage
Speaking of which, why don't we review the basics of metamorphosis.

Metamorphosis stems from the Ancient Greek word for "transformation."

Complete metamorphosis describes arthropods that have four distinct stages: egg, larva, pupa & adult.

Amphibians also metamorphose, but their process is considered gradual metamorphosis, since there are no distinct stages in their development.

The process is really quite miraculous when you think about it!

A newborn Hickory Horned Devil - remember the caterpillars that grow to the size of hot dogs? They have to start somewhere!
Aside from Lepidopterans (butterflies and moths), flies (Diptera), dragonflies (Odonata), beetles (Coleoptera) and ants (Hymenoptera) also undergo complete metamorphosis.

Okay, back to our tiny charges...

All you really have to do for them at this point is protect them from predators (caterpillars provide food for many animals!), clean up after them and keep their food fresh.

It's better to keep them outdoors, if you have a safe place for them out of direct sunlight and sheltered from the weather. They never seem to thrive as well if kept in an air-conditioned building. I usually set them down in an open terrarium on my front porch.

When they are this small, they will only need their food replenished every few days, as it will stay quite fresh in the bag. As far as cleaning up after them, you will notice tiny black grit collecting in the container. This is, of course, their poop (or frass, if you want to get technical). This also increases 1,000 times in size, by the way. To clean out the container, simply remove the leaves the caterpillars are on, and shake out the frass.

Something else you will notice is the caterpillars themselves will undergo dramatic transformations over the course of their development. These stages are referred to as instars.

When they first hatch, Cecropia caterpillars are completely black. Much like a snake, whenever they outgrow their skin, they shed it and emerge with a fresh one. Sometimes they will emerge a different color.

These are 3rd or 4th instar Cecropias
Often times these color changes help to better camouflage them as they grow.

One caterpillar with dramatic instars is the Spicebush Swallowtail caterpillar. When they first emerge, they resemble a bird dropping. A few instars later, they begin to look like a snake.

Both of these are meant to fool predators.

As the Cecropias grow, they will eventually need a different housing arrangement. Here are some older caterpillars that our Regional Naturalist brought by a few weeks ago.

These are early instar Promethea Moth caterpillars surrounding a week-old Cecopia
Late instar Promethea
When they get this big, they really need more room to spread out, as well as better air circulation. I've found that if they are kept closed up in a plastic bag they begin to get fungal and bacterial infections more easily.

The easiest way I've found to do this, is to take an empty sour cream or margarine tub, slice x-shaped holes in the lid, add water to the container and push the branches into the holes. This not only keeps the branches watered and in a more natural upright position, but the lid prevents the caterpillars from drowning (ask me how I know).

Propping the terrarium on its side gives enough vertical room for this arrangement, and still allows you to close them up to protect them from predators (mainly birds, at this point).

So how long do they grow? It depends on the species and environmental conditions, but most caterpillars complete their growth within 6-8 weeks.

It should also be noted that many of the caterpillars will not survive. The reason moths lay so many eggs is that, like I mentioned before, caterpillars are a coveted prey item, especially for all of those birds who need easy protein to feed their growing babies.

This jumping spider managed to snag one of my newborn Blinded Sphinx babies when I left the top off
Some will always die for mysterious reasons. Regardless, I always release a good number of them as they grow, to help keep them from getting too cramped.

Another option is to get mosquito netting and wrap limbs to make enclosed feeding areas for them. It offers some protection, and is a less labor intensive method of raising them.

I'll keep you posted on their progress, and next time I'll discuss more in depth about life as a caterpillar.

Ready, set, GROW!


  1. This might be a silly question - but do you seal the plastic bags? Do they not suffocate? I feel like I may be missing something.

    1. That's a perfectly good question. :) Insects are so tiny and use so little oxygen in relation to their body size, it would take a LONG time for them to run out in that sized space. The bag usually gets opened at least once a day, anyhow.

  2. Wow, so neat! I'm itching to try my hand with some of these, but I have to find them first! Can you keep multiple species together or will they...bug...each other? Bhaha.. sorry, I couldn't resist. :P

    1. Lol! Most of the time they don't mind each other, as long as they don't encroach on their space.

  3. Wow...1,000 times growth, that is insane! What an amazing creature!

    Thanks for linking up with Green Thumb Thursday. I hope you'll join us again this week!