Larval Leftovers

Every September, for as long as I can remember (or at least well more than a decade), I have been collecting caterpillars in preparation for the annual BugFest event at the North Carolina Museum of Natural Sciences. It is always great fun to share these larval lovelies with the thousands of visitors that make the pilgrimage to this super annual event. But, there is a price to pay – the care and feeding, and eventual release, of all the stars. And so it was, again this year. Given the timing of the event in mid to late September, it is always touch and go as to whether we will find enough caterpillars or if the ones we do find will actually make it to the big day without pupating. So, here are a few brief stories of some of this year’s stars, or almost stars, as the case may be.

Stinging Rose Caterpillar 1

Stinging Rose Caterpillar (click photos to enlarge)

I was very happy when I found this unusual beauty, a Stinging Rose Caterpillar (Parasa indetermina) on a willow, the week before BugFest. These odd-shaped and brightly colored larvae are one of the stinging caterpillars, and this one was sure to be a crowd-pleaser. But, as is often the case when dealing with nature, it was not to be.

Stinging Rose Caterpillar with parasite cocoons

Parasitic wasp cocoons on the Stinging Rose Caterpillar

A few days before the big event, it succumbed to a common caterpillar threat, the emergence of parasitic wasp larvae that quickly spun cocoons, coating the caterpillar’s body with what look like tiny cotton swab tips. I was going to take it anyway, to share that unusual aspect of the ecology of life as a larva, but, the day before the event, the caterpillar shriveled up to nothing, cutting short this one’s chance at fame. These parasites are fairly common and I always find a few caterpillars that already have the cocoons present when I am out collecting. But it is particularly disappointing when you collect something unique, only to find out later that the parasitic larvae were already at work, but you just could not tell until they popped out in a moment reminiscent of the classic scene from the movie Alien.

Spiny Oakworm shedding

Spiny Oakworm shedding its skin

In what looks like another scene from a space aliens movie, I was witness to one of the miracles of the caterpillar world when one of my captives managed to molt under my care. This one, a Spiny Oakworm (Anisota stigma), was still for almost two days and I suspected it was undergoing changes related to either molting or pupation. Right before packing up for the event, I saw this change-of-clothes act. Note the dramatic difference in color between the freshly molted larva and its cast skin. The caterpillar gradually darkened just in time to share its new look with the crowds.

Puss Caterpilar underside

Underside of Puss Caterpillar

I already posted on my experience with one of the most notorious of the stinging caterpillars, the Puss Caterpillar. When I was transporting it for release (my goal is to release these critters back into the general area where they were collected each year) I placed it in a plastic container like the ones you buy fresh salad in at the grocery store. When the larva crawled around the clear sides it provided me with a great view of the underside of this furry beast, something you don’t normally get to see.

Monarch larva chewing leaf

Monarch caterpillar chewing milkweed leaf

A friend loaned me a couple of large Monarch Butterfly larvae, and this one was busy all during the event chewing the edges of a Common Milkweed leaf. I grabbed a moment during the busy day to get a portrait of the feeder in action.

Spiny Oak-Slug top view

Spiny Oak-Slug during the event

Several of the stars started to wander off their food plants during the event. This is usually a sign that their time as a caterpillar is coming to an end and a pupa is on the way. Most larvae go through what I call a “walk-about” stage for several hours before starting to pupate. If they are not contained, they will wander off to some suitable spot and undergo yet another miraculous change in their extraordinary life cycle. And so it was with one of the small beauties of this year’s event, a Spiny Oak-Slug.

Spiny Oak-Slug cocoon

Spiny Oak-Slug cocoon

But, at least it waited until after the event to complete the change from dazzling caterpillar to drab cocoon. It should overwinter in this state and emerge next spring.

Luna Moth caterpillar

Luna Moth caterpillar

I found several large Luna Moth caterpillars the week of the event, and, as usual, a few pupated before the big day. And a couple decided to start the big change during the event itself and had to be confined to caterpillar detention (aka the pupation cage).

Luna Moth larva changing color prior to pupation

Luna Moth larva changing color prior to pupating

Like many species, Luna larvae undergo a noticeable color change right before they start spinning a cocoon, in this case, changing from brilliant green to a pinkish-brown color.

Spicebush Swallowtail nearing pupation

Spicebush Swallowtail in walk-about phase

Another color changer is one of my favorite caterpillars, the Spicebush Swalllowtail. They, too, are bright green, along with their uncanny false eye-spots and other markings. When they start the walk-about phase, they gradually change to a more yellow-orange base color.

Spicebush Swallowtail nearing pupation 1

Spicebush Swallowtai

You can see why these guys are one of my favorites.

Spicebush Swallowtail prepupa

Spicebush Swallowtail prepupa

Once they find a suitable site, they begin laying down their two silk attachment points to form a prepupa. That usually lasts about a day, and then they shed their skin one last time, and, voila, a chrysalis appears.

It is always a bittersweet time when BugFest is over and I release all my specimens. I know the chills of winter will soon be upon us and it will be several months before I can once again observe and photograph one of nature’s most amazing life forms.

 

 

 

 

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