Leading a Double Life on the Edge

There is more both of beauty and of raison d’etre in the works of nature- than in those of art.

~Aristotle (384 BC-322 BC)

The adaptations of insects in our yard are both beautiful and incredible. Here is a little more on some leaf edge caterpillars discovered the past few days…

Double-toothed prominent

Double-toothed prominent on elm leaf (click photos to enlarge)

One of the most exciting finds was a group of double-toothed prominent caterpillars (Nerice bidentata) on an elm sapling. These guys are amazing in that they have noticeable fleshy “teeth” on their dorsum that mimic the double serrated leaf edge of elm leaves, their host plant.

Double-toothed prominent early instar 1

Early instar of double-toothed prominent larva

Several of them molted over the past few days and I noticed what seems like a slight change in behavior between the different sizes. The smaller larvae are somewhat darker in color and seem to feed along the leaf edges in a more exposed position.

Double-toothed prominent on small leaf

Their color and pattern aids in the deception

The brown tips of the prolegs match brown spots along the mid-vein of the leaf.

Double-toothed prominent close up

Later instar

Larger larvae appear lighter in color, and seem to feed at an angle that puts them slightly under the leaf. The leaf underside is lighter in color than the top, so maybe this is why. The larvae also have angled stripes along their sides which mimic the venation of the leaves, adding to their effective disguise.

Double-lined prominent

Double-lined prominent on elm leaf

While looking at other elm saplings, I came across another species that seems to mimic both the leaf edge and the twigs of its host plant. When viewing the dorsal surface of a double-lined prominent (Lochmaeus bileneata), the reddish-brown color resembles an elm twig.

Double-lined prominent 1

The light stripes may mimic the leaf petiole

When viewed from the side, the white and yellow stripes along the cater[pillar’s body look like the mid-vein of a leaf, and the brown resembles dying leaf tissue.

Double-lined prominent 2

Even the head stripe helps in the disguise

The feeding position (head towards the tip of the leaf, body along the mid-vein) reinforces the effectiveness of the cryptic pattern and colors, with even the stripes on the head capsule resembling part of the angled leaf venation. I suppose it should come as no surprise that I can spend hours wandering around the yard, amazed by the small wonders all around me. I hope you all can spend some time outside this holiday weekend and discover wonders of your own.

Life on the Edge

In the struggle for survival, the fittest win out at the expense of their rivals because they succeed in adapting themselves best to their environment.

~Charles Darwin

Unicorn caterpillar wide view

Unicorn caterpillar positioning itself in a portion of the leaf it has eaten (click photos to enlarge)

I shared some images last week of one of my favorite moth larvae, the unicorn caterpillar. Their shape, coloration, and behavior allow them to blend in remarkably well with their environment. Turns out, they are not alone in their ability to hide in plain sight along the edges of leaves. It is a common strategy of many caterpillars, and I was delighted to find a few other species of leaf edge mimics in the yard over the past few days.

Wavy-lined heterocampa wide view

Wavy-lined heterocampa on hophornbeam leaf

One of the more remarkable leaf edge look-alikes is the wavy-lined heterocampa, Heterocampa biundata. It is variable in color, but frequently has brick red and white splotches along its sides that resemble necrotic leaf tissue. I assume this is a particularly effective camouflage for species that live during late summer and early autumn when many leaves are pock-marked by such splotches.

Wavy-lined heterocampa

Blending in to a hickory leaflet

This species is a generalist feeder on a variety of woody plants (I found them on two species of trees here in the yard). In addition to the leaf splotch patterns on their sides, they tend to align themselves along leaf edges in the areas of leaf they have devoured. The slight bump along their dorsal surface outline helps with this camouflage by making them look more like a leaf edge contour.

Chestnut Schizura on Viburnum nudum side view 1

It requires a careful look to pick these leaf edge mimics out of the background of green

Another excellent leaf mimic is the chestnut schizura, Schizura badia. I found a few feeding on the leaves of a possumhaw, Viburnum nudum. They tend to place themselves inside the outline of portions of a leaf they have consumed, once again making for a well-camouflaged caterpillar.

Chestnut Schizura on Viburnum nudum side view

A closer look

They also have brownish splotches that mimic dying leaf tissue.

Chestnut Schizura on Viburnum nudum

Dorsal view

This species is characterized by a diffuse yellow saddle over the dorsum of the abdomen and a large, irregular-shaped, brown patch on the sides.

Chestnut Schizura on viburnum leaf

A close relative of the unicorn caterpillar

It is a close relative of the unicorn caterpillar and also has the ability to shoot a blend of acids at would-be predators. The defensive spray comes from a thoracic neck gland and can be shot a distance of up to several inches.

Small-eyed sphinx caterpillar on cherry wide view

Small-eyed sphinx larva

Although not a leaf edge mimic per se, the other species I found yesterday does a good job of looking like a common leaf pattern on its host, wild cherry. I am pretty sure this is the first of its kind I have found in my years of caterpillar hunting. It is a small-eyed sphinx, Paonias myops.

Small-eyed sphinx caterpillar on cherry

The red splotches mimic leaf spots on wild cherry

The red splotches certainly are excellent mimics of the pattern on the underside of many wild cherry leaves this time of year. The behavior of this species helps with this deception  as it tends to stay underneath leaves (where the leaf splotches are most noticeable) during the day and then comes out to feed mostly at night. Wagner, in his excellent reference, Caterpillars of Eastern North America, wonders if the spots are more apt to occur on individuals feeding in the autumn, when cherry leaves tend to have more splotches. I continue to be amazed at the intricacies of nature found just outside our door. More on some other leaf edge larvae in my next post.

Seeing the Wild in Wild Cherry

The most beautiful gift of Nature is that it gives one pleasure to look around and try to comprehend what we see.

~Albert Einstein

There is a wild cherry (Prunus serotina) sapling just outside our screen porch that is a favorite spot for all sorts of natural events. Wild cherry is a great host plant for a variety of moths and butterflies so I let this young tree grow in a spot too close to the house to ever reach any height just so I can keep track of the comings and goings of its tenants. It has been a busy place these past few days.

red-spotted purple early instar

Red-spotted purple early instar larva (click on photos to enlarge)

Throughout the year, I can always count on seeing some sign of one of the primary occupants of this species of tree, the red-spotted purple butterfly, Limenitis arthemis. They lay their eggs at the tip of cherry leaves, and the larvae feed on the leaves through their entire caterpillar and chrysalis stage, appearing as bird poop mimics. And they even overwinter on the plant, with the third instar larvae of the fall generation making tiny sleeping bags, or hibernacula, by cutting away much of a leaf and rolling the base into a hollow tube where they spend the winter. Next spring, when the cherry leaves first sprout, the tiny larvae will emerge form their tube, begin feeding on the fresh leaves, and begin the whole cycle again. In the photo above, the larvae has already attached the leaf to the twig with silk (so the leaf fragment remains on the tree all winter) and is just beginning to curl the base of the leaf with even more silk (silk strands shrink as they dry, pulling the leaf together).

red-spotted purple hibernaculum 1

One day later, a hibernaculum!

By the next day, the larvae had finished constructing its hibernaculum and was resting inside. I’m a bit surprised it has constructed this so soon as there is still plenty of time for it to grow, pupate, and start another generation before cold weather. But, there are not many leaves left on this tree at this point, so maybe caterpillars can take a cue from food availability and go ahead and go into a resting phase for the winter.

red-spotted purple last instar

Last instar red-spotted purple caterpillar on a different sapling

On a nearby cherry sapling, I found a much larger red-spotted purple larva which will soon, no doubt, form a chrysalis.

white-marked tussock early instar

White-marked tussock moth larva, early instar

Back at the original tree, there were a couple of other caterpillars to observe. One of my favorite finds this time of year is the white-marked tussock moth caterpillar, Orgyia leucostigma . They remind me of a combination caterpillar and toothbrush, due to the four prominent tufts protruding near the head, plus the two black-colored tufts of setae out front that resemble some fancy flossing tool.

white-marked tussock just after molt

White-marked tussock moth larva and shed skin

Nearby was another one that had just molted. This species is a generalist feeder, so I find it on a variety of plant species around the yard.

Unicorn caterpillar second instar

An early instar unicorn caterpillar

Nearby was another of my favorites, an early instar of the unicorn caterpillar, Schizura unicornis. These guys do an amazing job of blending in with the edges of the leaves of whatever they are feeding on. As I looked around, I found a few more…and that will be some fodder for my next post.

 

Summer Cats

Nature will not be admired by proxy.

~Winston Churchill

Seems as though my schedule (and the heat) have kept me from some of my usual yard patrols, so I finally went out the other day for a walk-about to see what I could see. It started with my eye catching something out of place on a hickory sapling near the gate…a bright green spot at the edge of a leaf…

Caterpillar head

Caterpillar head peaking out from behind a leaf (click photos to enlarge)

When I walked over, I could see by the distinctive triangle-shaped head, framed by a pair of yellow stripes, that it was an old acquaintance – the larva of a walnut sphinx moth, Amorpha juglandis.

Walnut sphinx larva

Walnut sphinx larva feeding on hickory leaf

I did a short blog post on this cool species a couple of years ago when I found out it has an unusual ability…it is one of the few caterpillars that can make sounds! Researchers discovered it can make a high-pitched whistle by quickly expelling air out of its eighth pair of spiracles (the small breathing tube holes along the sides of caterpillars). Studies have shown that the sound may be enough to scare off potential bird predators.

Walnut sphinx larva 1

The walnut sphinx larva is distinctive in its appearance and abilities

Even though I probably disturbed this little guy while taking its picture (they usually feed on the underside of leaves so I had to flip him over for a full profile pic), I heard no whistle. I can’t decide whether their sound is outside my range of hearing (like many warblers) or these caterpillars just realize I am a long-time fan of their kind and present no threat. After photographing this species, I decided to walk around for a few minutes to see what else I might find.

Walnut caterpillars

Walnut caterpillars

Just a few feet away on another hickory sapling, I found an aggregation of strange, hairy larvae that turned out to be walnut caterpillars, Datana integerrima. What made me notice was a couple of leaves that had been heavily chewed. As I got closer, I could see something that looked like my barber had glued some of my trimmings all over a couple of black worms. When I touched the leaf, they quickly arched into a c-shape, a classic defense pose for members of this genus of caterpillars.

Walnut caterpillars 1

The larvae had just molted

I flipped the leaf to get a better look and found that they had all just molted. This is typical for this species, which is known to move down out of the trees where they are feeding in masses in order to molt. Walnut caterpillars generally have at least two generations per year in the south and can periodically be serious defoliators of localized populations of black walnut, pecans, and various species of hickory. I have never seen them cause significant problems in this area as they seem to be controlled fairly well by natural predators and parasites.

So, in just a few minutes time just outside my door, within a span of less than thirty feet, I was rewarded with glimpses of two fascinating species that share my habitat. It is always good to be reminded that to really enjoy nature, you have to be out in it.

 

 

 

 

 

When Worms Aren’t

The worm poop is raining down like a black sleet storm. Got to remember not to open mouth while looking up.

~Ken in Texas, on Unofficial Allis Chalmers Forum, talking about Catalpa Worms

A little over a month ago, I received an email from a neighbor about some caterpillars that were “munching their way thru one of our catalpas”, along with a photo. He also mentioned he had heard these were considered “the gold standard of live bait.” And he was right, they were, indeed, the famed “catalpa worms” (also called catawba worms), a species I had always wanted to see up close. I had seen evidence of their feeding many times, but the caterpillars were always too high up in the tree to photograph. As luck would have it, time slipped away and I did not get down to my neighbor’s place in time to see that batch of caterpillars. But, last week, I went down to get a couple of plants at his nursery (Cure Nursery, a native plant nursery) and was stunned to see another group of early instar caterpillars on those same Catalpa trees.

Catalpa tree branch showing caterpillar feeding

Catalpa tree branch showing caterpillar feeding (click photos to enlarge)

I was stunned because I always assumed there was only one generation per year, as the few trees I have seen around here are always stripped of all their leaves by June or July. In fact, the caterpillars will probably not survive on my neighbor’s trees because the leaves have all been stripped and have barely started to leaf out again. Those few leaves will surely not be enough feed all of these caterpillars. So, I gathered a few of the larvae up and managed to collect a few leaves from sapling sprouts at another roadside location.

Catalpa Sphinx are colonial feeders

Catalpa Sphinx are gregarious feeders in early stages

These boldly patterned larvae are actually the caterpillars of the Catalpa Sphinx, Ceratomia catalpae. Female moths lay large clusters (sometimes numbering in the hundreds) of eggs only on Catalpa trees. Early instars of the larvae feed in groups, turning to solitary feeding in their later stages.

Catalpa Sphinx larva

Catalpa Sphinx larva

As with most members of the Family Sphingidae, the larvae are adorned with a prominent tail spike, which seems exaggerated on the early instars.

Catalpa Sphinx pair of larvae 1

Pair of feeding larvae

Catalpa Sphinx larvae heads

They are eating machines

And, like most caterpillars I have seen, these guys are eating machines. In the short time I was photographing them, just a few managed to consume about half of one of the large leaves I collected. And when they eat, they poop (you can see some frass, caterpillar poop, in the first photo of this pair). So, if you are standing under a large Catalpa tree having perhaps hundreds of large caterpillars up in its branches, I suppose it can sound like rain pouring down. Caterpillars eventually climb down the tree trunk and pupate in the ground nearby. And, surprisingly, it is common to have two or more generations in a season.

Catalpa Sphinx pair of larvae

Fishermen swear by the later stages of these larvae as fish bait

In looking online, it seems the large (up to 3 inches) caterpillars are, indeed, a favorite of fishermen. In fact, their value as fish bait (especially for bass and catfish I am told) was mentioned when the species was first described in the 1870’s. Apparently, the skin is tough enough to hold the larva on a hook better than many live baits. So, whether the caterpillar is a pest when it defoliates your Catalpa, or a valuable commodity, depends on your perspective, as is so often the case when it comes to things in nature. For me, it’s enough to just have the chance to finally see some of these beauties up close.

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.