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.





Caterpillars as Art

“The caterpillar does all the work but the butterfly gets all the publicity”

George Carlin

I’m sure that’s just how some caterpillars feel, under-appreciated at best, reviled by many a homeowner at worst. Caterpillars are often seen as those critters that “eat my plants” without the person making the connection to their necessity in order to have the beautiful butterflies (and moths) that visit our gardens and pollinate so many plants. But I think caterpillars are just as beautiful as their adult forms and here are a few images that I hope will convince you of that as well.

Curved-lined Owlet backlit

Curve-lined Owlet backlit

By moving my light source around using my macro twin lights, I can get dramatically different results.

Curve-lined Owlet silhouette

Curve-lined Owlet silhouette

By placing a white piece of foam core as a backdrop, you can highlight the outline.

Hog Sphinx wth light from behind

Hog Sphinx

Some species have a translucent quality when light is shined on them from behind or the side.

Black-etched Prominent close up of legs

Black-etched Prominent close up of prolegs

A close up shot often reveals beautiful combinations of the larva and its plant.

Spicebush swallowtail on leaf pad

Spicebush Swallowtail caterpillar

And the winner in the make-up artist category is….the Spicebush Swallowtail. This is one caterpillar that looks like an artist painted it with bright colors and patterns. It hides in a leaf shelter pulled together by stretching silk across the leaf. Then it tucks its real head and arches making the fake eyes more pronounced to discourage predators.

Spicebush swallowtail fake eye

Spicebush Swallowtail fake eye

The level of artistic detail on the fake eye is what amazes me – there is a light spot that makes the “eye” seem moist, heightening the illusion.

So, get outside this weekend and take a moment to look closely and appreciate the wonder and diversity that surrounds us. Take a moment to sit with a caterpillar and admire it. Prepare to be amazed.

Cool Cats

“Teaching a child not to step on a caterpillar is as valuable to the child as it is to the caterpillar.”        Bradley Millar

Caterpillars are cool. I have been fascinated by these diverse and sometimes outlandish creatures for decades and have found them to be one of the best gateways for introducing people to the wonders of nature. I have used them effectively in teaching teachers, students, and the general public in my thirty year career with state parks and the museum. Their often unusual shapes and behaviors make them instantly appealing, they are fun to raise, and almost everyone that witnesses the miracle of metamorphosis is changed in some way. Tomorrow is the annual special event at the museum, BugFest, where we get to showcase caterpillars (and lots of other types of interesting invertebrates) with thousands of visitors. Several staff plus a few volunteers like me have been out looking for caterpillars this past week to share at BugFest. We have found a good variety but I want to highlight three of my favorites.

Yellow-shouldered Slug 1

Yellow-shouldered Slug (click on photos to enlarge)

I posted on one of the more exotic slug caterpillars last week, the Saddleback. There are more than twenty species of slug caterpillars in our region, and there are some that do not have the stinging spines of the Saddleback. The Yellow-shouldered Slug is actually one of the more mundane of the group in appearance, but I always enjoy finding any of this peculiar clan. This species apparently has stinging spines in early instars (an instar is the stage between molts), but lacks them in the final one. Slug caterpillars tend to have more instars than most caterpillars – from 7 to 9, instead of the usual 5 of most species. Not sure where this one is in the process although it is still pretty small.

Black-etched Prominent 3

Black-etched Prominent

The Prominents are another interesting group. Several have greatly elongated anal prolegs which resemble two tails. This Black-etched Prominent was feeding on a willow when it was discovered due to the presence of chewed leaves.

Black-etched Prominent 5a

Black-etched Prominent feeding on willow leaf

They do have a remarkable camouflage that mimics the leaf color and shape, even to the detail of having a faux mid-vein-like stripe along their sides. But if pretending to be a leaf doesn’t fool a potential predator or parasite, this prominent has a couple of other defenses in its arsenal. The caterpillar can rapidly pump fluid into the two “tails” when it is agitated thereby greatly increasing their length. It quickly arches them over the body and whips the air with them which is probably especially effective against small flying parasitic wasps and flies.

Black-etched Prominent face

Black-etched Prominent “face”

If further alarmed, the caterpillar rears back and arches its head toward the intruder, revealing markings that look like a large false head with dark eyes. It also opens and closes its mandibles in a threat display. Ultimately, this, and several other prominents, may result to chemical warfare. They can shoot an acid spray from a gland underneath the head region. I have not yet experienced this so am unsure if it deters something like a large mammal with a camera, but will let you know if and when.

Curved-lined Owlet as dead leaf mimic

Curve-lined Owlet as dead leaf mimic

Then there are the caterpillars that I have seen in David Wagner’s field guide, Caterpillar’s of Eastern North America, and wished I could see first hand because they are so beautiful or bizarre (yeah, it’s true, I do think about such things). The Curve-lined Owlet is one of those species. And then, on the same day as the encounter with the Bobcat I reported in the last post, my friend found one of these Owlets on its host plant, Greenbrier (or Catbrier, Smilax sp.). And bizarre it is.

Curved-lined Owlet dark green background

Curve-lined Owlet on Greenbrier tendril

This caterpillar is a dead leaf mimic. It is very slow in its movements and will gently quiver from side to side when disturbed, much as a dead leaf would do in a slight breeze. The unusual elongate projections coming off the dorsal side make sense when you see the caterpillar in its environment – the tendrils of its host plant, Greenbrier, have similar curves, and the rolled edges of dying leaves are similar in color and shape. After BugFest, I will return this and a couple of the other caterpillars found down east to their rightful home (either as larvae or pupae). Every effort is made to return the larvae to the proper environment after they are used for educational purposes. Now, if I could only find that one on page 270 that mimics the color and shape of a cluster of green grapes.