~Quote attributed to a student in an introductory entomology course
We discovered a small caterpillar last week that was adorned with some unusual accessories, and that usually isn’t a good thing if you are a caterpillar. I think it was either a variable oakleaf, or a double-lined prominent caterpillar. Both are common species that feed on a wide variety of trees and shrubs.
Caterpillar adorned with green accessories (click photos to enlarge)
I have seen these bright green baubles attached to a few other caterpillars over the years, and it never ends up well.
Not the type of fashion accessory you want if you are a caterpillar
They really are beautiful in shape and color when you take a closer look. The first time I saw a caterpillar with these green blobs on its side was a few years ago. I thought they might be some sort of strange cocoon of a parasitic wasp. I was close…they are actually the larvae of a tiny parasitoid wasp in the family Eulophidae.
Eulophid wasp pupae next to the dead host caterpillar
After watching the caterpillar for a few days, I came back to find a strange array of tiny black blobs near the shriveled caterpillar carcass.
The small piles of yellow “stones” near the pupae are actually waste products
When I looked at my macro images, the small black blobs looked like some sort of macabre lawn recliner, with a tiny pile of rocks at the base. The black blobs turned out to be wasp pupae lying on their backs, and the piles of rocks are the waste products excreted by the wasp larvae prior to pupating. These are parasitoid wasps in the genus Eulophis. They feed inside their caterpillar host, mature, and then pupate in a group near the carcass of their victim. The excellent reference by Eiseman and Charney, Tracks and Signs of Insects and Other Invertebrates, refers to these bizarre creatures as “tombstone pupae”. I find a lot of these clusters of Eulophis pupae on the undersides of sycamore leaves this time of year.
Another strange way to go
A few days ago I found another caterpillar that had met what seemed like an unusual death.
At first, I thought a fungus had attacked this caterpillar
The fuzzy texture initially caused me to think some sort of fungus had killed it.
And what are these tiny black pellets?
But when I knelt down and took a closer look, I could see what looked like pupae inside the fuzz, as well as some tiny black pellets or balls stuck to the threads. What the heck is this? Going back to my reference book (mentioned above) for all things strange in the invertebrate world, I found a plausible answer. This caterpillar had been killed by another type of parasitoid wasp in that same family, but most likely in a different genus, Euplectrus. These larvae tend to form a cluster on the dorsal surface of the living caterpillar. When they finish feeding, they move to the underside of their deflated host, and arrange themselves in a row, and prepare to pupate. They create a gauzy, web-like cocoon, which attaches the caterpillar remains to the plant and provides a protective covering. The black pellets are the meconium, or waste products, cast out by the prepupa. It looks as though there wasn’t quite enough room under the carcass for all the wasp larvae to pupate, so some had to be elsewhere in the fuzzy covering.
How bizarre…and it is all happening just outside my door!
Red-spotted purple butterfly (click photos to enlarge)
Well, that is certainly the case for at least one species of butterfly here in the woods… the red-spotted purple, Limenitis arthemisastyanax. This common species is probably not considered beautiful by most observers during its pre-butterfly stages.
Early instar of red-spotted purple caterpillar
It is a bird poop mimic throughout its early life, especially from the third instar larva all the way through the chrysalis stage.
The larval stages are bird poop mimics with light splotches on a dark background
Last instar red-spotted purple caterpillar
I found a late instar caterpillar on a wild cherry recently and decided to watch it in hopes of finding the chrysalis when it crawled away.
Pre-pupa of red-spotted purple (note silk pad attachment point at rear of body – top in this photo)
The next day the larva was gone. They often crawl off the plant where they have been feeding and look for a vertical surface to climb. They make a silk pad, attach themselves and hang from it, forming a pre-pupa that lasts about 24 hours. Then, the last molt of the caterpillar skin occurs, revealing the chrysalis. Luckily, I discovered the pre-pupa attached to the basement door frame. The caterpillar had crawled a distance of about 25 feet. The next morning I hoped to see the chrysalis.
Dead pre-pupa the next morning
But, what I found instead was a dead, blackened pre-pupa. I have seen this shriveled black appearance in other caterpillars when they have been parasitized by various things from tachinid flies to a virus. I watched it the next couple of days and never saw any sign of something emerging, so I am guessing this is a viral infection of some sort that killed this particular larva. I was disappointed, but, to my surprise, I discovered a chrysalis a few days later while pulling weeds in the front yard.
Red-spotted purple chrysalis (still a bird poop mimic)
The red-spotted purple chrysalis looks like damp bird poop hanging from a twig. One odd feature is the small round disc that sticks off the side of the chrysalis at about the mid-point. I have never been able to figure out what this is in relation to the butterfly that emerges. I decided to try to keep tabs on this pupa over the next few days to see if I could get lucky and photograph the newly emerged butterfly.
Freshly emerged red-spotted purple butterfly
Sometimes you just get lucky, and the next morning when I checked, there was a freshly emerged butterfly clinging to the shell of its chrysalis. They usually hang on for an hour or so while they pump fluid into their wings (via the veins), and allow the wings to become firm for flight. This one’s wings were fully formed, so I found it just in time to get a few images.
A closer look at the head of the butterfly shows a coiled proboscis
I moved around taking photos. The butterfly occasionally moved in response, flapping its wings in preparation for its initial take-off. The colors on fresh butterflies are so vibrant!
The colors don’t quite match the butterfly’s name
But, admiring this fresh beauty reminded me that the colors don’t really match the rather odd name of this common species – the red-spotted purple. I wonder why it isn’t called the orange-spotted blue butterfly instead. And, come to think of it, while I am renaming things, perhaps I should change the title of this post to From Poop to Pretty. Both changes are perhaps a bit more descriptive of the unusual life history of this fascinating insect.
Nature taking its course – hunter and prey, the endless circle of life and death.
~Stephanie Meyer
Melissa found some cool caterpillars on a Viburnum this weekend while we were walking in a city park in Richmond.
Hummingbird clearwing caterpillar on Viburnum sp. (click photos to enlarge)
I walked over to take a look and saw a beautiful hummingbird clearwing larva, Hemaris thysbe, in the classic defensive pose of most sphinx moth caterpillars – front of body reared up, head tucked in, body aligned along the twig or mid-vein of a leaf. Suddenly, a huge European hornet, Vespa crabro, appeared and went straight for another caterpillar on the shrub, another hummingbird clearwing.
European hornet attacking a caterpillar
I managed two quick pictures, and the hornet flew off, carrying its prize back to its nest, where the defeated caterpillar was sure to be chewed up and fed to some hungry wasp larvae. We just stood there, amazed at what we had witnessed. When I looked at the image the next day, I noticed there was another, smaller caterpillar on the same leaf (look just to the left of the clearwing’s “horn” and you can see another small, green caterpillar).
European hornets first appeared in the United States in the mid-1800’s and have since spread throughout most of the East. They look like a very large (up to 1.5 inches) yellow jacket, but are more brownish yellow in overall appearance. We didn’t have time to stick around, but I would not be surprised if that same hornet didn’t come back and search that shrub again, perhaps finding one or more other victims to carry back to the nest. Amazing how a scene in nature can change in an instant.
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 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).
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.
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 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 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.
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.
I seemed to have reached a new world, so wild a place…far away from human society.
~Henry David Thoreau, on swamps
Sunset from the town dock in Columbia, NC (click photos to enlarge)
Columbia, North Carolina, that is. We spent several days in this beautiful little town last week, part vacation, part getting out to see some of the region for the trails project I am working on with NCLOW. It didn’t help that it was one of the hottest weeks of the summer, but it did help that we spent much of it on the water. And this region has lots of water, from Lake Phelps, the second largest natural lake in North Carolina, to the Scuppernong River, to the numerous creeks and sloughs that beckon paddlers to explore. So, we decided to take our kayaks, throw them in where we could, and see what we could see in a few days on the water. First stop, was the NW Alligator River.
NW Alligator meanders up into Pocosin Lakes National Wildlife Refuge from Hwy 94
I had scouted out some potential put-in points (they are few, unfortunately) so we decided to put in at what looks like an old boat ramp near where Hwy 94 crosses this section of river, about 14 miles south of Columbia. The access is now flooded, but there is a substantial old dock at the site, indicating its past use, perhaps in logging or fishery operations.
We launched on the east side of Hwy 94 at an old boat ramp area
The lands surrounding this waterway have scattered trees, low pocosin vegetation, and a border of marsh grasses, including pockets of wild rice. Shortly after we passed under the Hwy 94 bridge, we spotted a bald eagle, who managed to stay with us much of the morning. The other wildlife highlight were several red-headed woodpeckers, flying between the many standing dead trees along the route.
A perfect day for paddlingDragonflies were our constant companionsCalm winds made for great reflections
An abundance of clouds made for beautiful reflections and a respite from the heat. After paddling about 1.5 miles, we came to the juncture of the SW and NW branches of the Alligator, and headed north. The path narrows after this, and we found ourselves going through patches of alligator weed and a grass of some sort, most likely maiden cane. Patches of the alligator weed looked as though they had been treated (this is an invasive species that can clog small waterways and is often treated chemically by local agencies).
Large patches of maiden cane finally blocked our path
After paddling another couple of miles, we finally reached a patch of the maiden cane that seemed too large to easily push through, so we turned around and headed back. Our total paddle was about 5 to 6 miles. The only sounds, other than fish jumping, dragonflies buzzing, and woodpeckers drumming, was the distant hum of some crop dusters spraying some of the huge farm fields down the road. I want to go back in colder weather , once some of the vegetation dies back, and see if I can make it all the way up to the refuge road system.
Friends recommended we try Riders Creek, near Columbia. It enters the Scuppernong River on the far left.
The next day we hit Riders Creek, a small tributary to the Scuppernong River about 2 miles south of Columbia. Finding a suitable launch site was again the challenge. The two road bridges didn’t offer much so we drove down a side road after looking at Google Earth and Melissa tested a large log on the bank of a roadside canal as a potential launch site. Nothing fancy, but it worked. This day, we had help, and another paddler, and were dropped off (there is no place to park at this makeshift put-in) and planned to paddle back to the canoe/kayak launch behind the Pocosin Lakes Visitor Center in town, a total paddle distance of a little over 5 miles.
The narrow creek is a beautiful paddle
The upper portion of the creek was my favorite as it is narrow and intimate, allowing us to see and hear the many bird species (prothonotary warblers, woodpeckers, and a great horned owl) and appreciate the small things along the way (an owl feather floating on the black water, the distinctive webs of the many black and yellow argiope spiders, and a clump of blooming cardinal flower adding a splash of brilliant red to the sea of green around us).
Large bald cypress trees are scattered along the creekRiders Creek joins the Scuppernong River about 1.5 miles south of Columbia
It was another great paddle, only a couple of hours long, but through a beautiful swamp forest, into the wide waters of the lower Scuppernong, and ending back in the picturesque town of Columbia. And, we were the only ones on the water, probably not unusual in this underutilized area of rich scenery and wildlife.
A group of palamedes swallowtails gathering nutrients from a somewhat unsavory source – scatA large canebrake rattlesnake along a back road
The palamedes swallowtails were out and about everywhere, and we managed to find a large canebrake rattlesnake crossing one of the refuge roads. I never tire of seeing this magnificent reptiles, and the refuge seems to have a healthy population.
The south shore of Lake Phelps
Our last stop was at the pocosin overlook at Pettigrew State Park, along the south shore of Lake Phelps. The clear water at Lake Phelps is such a surprise after spending a couple of days in the dark, tannin-colored waters of the region. It made for a refreshing dip on a hot afternoon.
NCLOW is looking at how we might help bring more tourists into this region to explore and enjoy its rich natural and cultural heritage. The waterways here offer scenic beauty, abundant wildlife, and the chance for quiet and uncrowded paddling. And Columbia is a beautiful town with a rich history and great potential. It is also home to Pocosin Arts, a real treasure of eastern North Carolina, whose mission is to connect culture to the environment through the arts. They offer a range of classes year-round, and are looking at ways to incorporate even more of their unique natural surroundings into their offerings.
One area that does seem to be getting a lot of attention from tourists is nearby Alligator River National Wildlife Refuge. Situated only about 15 minutes from the Outer Banks certainly helps fuel the busy summer tourist season on this refuge. It is known for its large population of black bears and for paddling opportunities along Milltail Creek. Several OBX outfitters provide canoe/kayak rentals and guided trips on the refuge. We decided to spend our last paddle day checking out this area. We drove to the main launch site at Buffalo City and were surprised to see 10+ vehicles, a crowd of people, and probably 20+ kayaks and canoes. Most people probably go downstream along Milltail Creek, so we decided to drive to another, lesser-known launch site upstream to seek some solitude.
Milltail Creek is obviously a popular paddle destination (Alligator River is on the far left of image)We launched upstream where Milltail Road crosses the creekFloating dock at the launch site
Besides the advantage of proximity to a large tourist population on the Outer Banks, the refuge also has two well-maintained launch sites on Milltail Creek. Ours had a neat floating dock that makes for a very easy launch. As we put in, a trailer with 6 boats pulled up, so I guess this site is not as unknown as I had thought. We quickly got out ahead of the group and for a few hours felt like we were the only people anywhere near this beautiful swamp.
Milltail Creek starts out narrow at this launch
Swamp iris occur in many places along the creekAnother beautiful day for paddling
We paddled for a few hours, traveling a total of about 7 miles out and back. The creek is rich in bird life and we saw lots of wood ducks, herons, and a few anhinga. My highlights were seeing a large alligator and a black bear along the route. The scenery is beautiful, it is incredibly quiet (if the jets are not buzzing overhead), and it is a great combination of solitude, ease of access, and abundant wildlife. I can see why it is such a popular destination.
A large bald cypress beckoned us over for a closer look
At one point along the way, I noticed a large bald cypress tree hugging the shoreline. Its large limbs draped down, seemingly embracing the dark water, making it look like a perfect place to pull in and escape the sun.
The giant trunk looked invitingA great place to relax in the shade
Sure enough, it offered a chance to climb out of our boats, relax for a lunch break, and it provided a Swiss Family Robinson moment for a couple of thankful paddlers.
Our three days of paddling showed me the great potential for the Scuppernong region, truly one of the jewels of wildness in our state. I hope we can help foster an awareness and appreciation of the incredible resources of this unique area, provide some economic opportunities for local entrepreneurs, and maintain the incredible natural heritage and beauty of this wild landscape. On our way home, we decided to check out an area that is making a strong effort to do just that.
Recently completed tree houses along the Cashie River in Windsor
The town of Windsor is located along the Cashie River, between Williamston and Edenton. The town is making a commitment to ecotourism along its waterways (see Destination Windsor) with kayak and canoe rentals, pontoon boat tours, a wetlands walk, and the recently completed tree houses. These two tree houses, funded in part by grants, are to be the start of a village along the river including a few more tree houses and a renovated campground. They hope to have these available for rent starting this fall. It looks like a great start to getting visitors to come to appreciate their natural surroundings. Let’s hope they prove successful and can pave the way for more such ventures in the wilds of eastern North Carolina.
The month of August had turned into a griddle where days just lay there and sizzled.
~Sue Monk Kidd
Last week, we spent 5 days in the wilds of eastern NC, a combination mini-vacation and working trip to further investigate the area around the Scuppernong River for the project I am working on with NCLOW. As you might expect, it was a tad warm (especially for the guy that loves cold weather), but we planned to be on or near water most of the week. Turns out, we are not the only ones that think that way. Returning to Columbia after a short excursion to the Outer Banks, we drove through Alligator River National Wildlife Refuge, in the hopes of seeing some wildlife. Temperatures had been hot all week with high humidity adding to the discomfort. We entered the refuge about 5:30 p.m., that time of day when wildlife begins to come out of the forest in search of an evening meal. Driving down one of the main gravel roadways, Melissa spotted something off to the side in the canal…a bear cooling off in the water, a bear bathtub.
Black bear cooling off in a canal on a hot August afternoon (click photos to enlarge)
It was a big bear, and it was just chillin’. When we pulled up, it glanced our way and then quickly went back into that chillin’ mode, eyes closed, almost a grin of cool relief on its face.
We could almost hear a sigh of relief in that look
The afternoon temperatures reached into the low 90’s that day, so I am sure this water, in spite of its less than desirable look, was quite satisfying. A black bear’s normal body temperature isn’t far from our own, around 98 to 100 degrees Fahrenheit (it is less during hibernation). The thick black fur is a good insulator, but can present problems in the heat of summer. And, like dogs, bears lack sweat glands, so they must use other means to cool off – panting, lying in the shade, digging day beds to lie on the cool ground, or taking a nice plunge in the water. I have seen bears cooling off before in canals at Pocosin Lakes NWR, but have never been this close to one seemingly so relaxed in the cool water.
The bear relaxed onto all fours when another car pulled up
Another vehicle soon pulled up, but the large bear did not seem concerned. It did shift its posture and sat down in the water with all four paws presumably on the muddy bottom.
The bear began to scrunch up its nose
After remaining almost motionless for a few minutes, the bear began to scrunch up its nose, revealing more of its teeth and tongue. We wondered what it was up to…trying to smell us (a third car had driven up at that point)? When I got home and looked at the images, I think I now know what was happening.
Was this face in response to biting flies?
The photos taken when the bear was scrunching up its nose show a couple of biting flies on its snout. Pictures prior to that (like the first three photos above) show none of the irritating insects.
A trickle of blood from a fly bite on his nose
The last few photos showed a tiny trickle of blood running off his nose. Look carefully at the previous image and you can see there was a fly in that spot. Guess I, too, would scrunch up my face under those conditions.
The big fella finally departs for the corn fields
After spending nine minutes with this big guy (no telling how long he was chillin’ in the canal before we arrived), he finally decided to head back up into the fields. I suppose he was headed for a nice corn dinner, and maybe some dense vegetation where those pesky flies couldn’t get to his sensitive nose.
It was a dark and stormy night, the rain fell in torrents…
~Edward Bulwer-Lytton, 1830
And indeed it was…last night. We barely beat a fierce thunderstorm as we drove back from dinner with friends in Chapel Hill. The sky was flashing with rapid-fire lightning when we arrived at our gate. I must have done something right recently, as just when I stopped at the gate, my driver’s side windshield wiper arm came apart. That would have been very problematic a few minutes earlier as we drove through a downpour. The rain let up just long enough for us to get inside, and then the sky opened up, and down it came. Something else must have come down somewhere as it wasn’t long before the power flickered, and then went out. A reminder of how really dark it can be out here in the woods…incredibly lively as well. Outside, I could hear another chorus of Cope’s gray tree frogs cranking up, another attempt at spreading the genes around. Most of the sound was coming from the water garden that sits half-empty, awaiting repair. I mentioned it in an earlier post as the source of the abundance of transforming tree frog tadpoles in the yard. And it looked like this would be another night for creating the start of many mini-frogs.
The rain let up so i wandered outside (sans camera, unfortunately) to see what all the fuss was about. I discovered a couple of reasons why it isn’t easy being a tree frog in love. A huge bullfrog was sitting over by one pool, the one without the breeding tree frogs. A guy that big can easily grab and swallow any tree frog that comes his way. That may be one reason the tree frogs are using the other pool, although I think it also has something to do with the thick cover of duckweed and other vegetation in the bullfrog pool. When I walked over to the tree frog pool, I saw another potential hazard to romancing frogs – a copperhead was dangling out over the pool, no doubt waiting for a love-struck frog to venture too close. By the way, that is one reason that pool will remain in a state of disrepair until colder weather arrives. I prefer moving all those stones after certain species are retired for the year.
The rain started up again so I retreated indoors. I soon heard a frog calling from out front, sounding like it was just outside the front door. I grabbed the camera and stepped out underneath the covered entrance way. The rain paused and I heard the frog call again, very close.
Cope’s gray tree frog sitting on walkway (click photos to enlarge)
I knelt down, and spotted the caller perched on the edge of our wooden walkway into the house. He was facing the to-be-repaired pool, the source of all of the other calling. Suddenly, he puffed his body a couple of times, as if taking a deep breath…
Gray tree frog calling
…and let go with a loud trill. His vocal sac extended for a second or so, just long enough for me to fire off a shot. I sat and watched him call a few more times before heading back inside. I figured he would soon hop off toward the other pool and join in the breeding frenzy. It is getting a little late in the summer for a full-on bout of tree frog breeding (the peak of activity is usually from late May – July), but you wouldn’t have known it last night. It has been a wet summer, and the frogs are taking advantage of every last storm, and last night it really seemed like it was raining cats and dogs (or frogs and toads at least). We probably had close to 2 inches of rain in the storm, and power remained out until about 5:30 this morning.
Right before heading to bed, I looked out the front door again. The calling frog had turned and was now facing me. I couldn’t let that obvious invitation go unanswered, so out I went with my camera one more time.
Catching his breath before another trill
I bent down a couple of feet away and he sized me up, but apparently had more important things on his mind…trilllllll!
Nice trill…
About that time, my camera battery died, so I headed back inside to a darkened house. I don’t know whether his efforts eventually paid off or not, but I felt lucky to have shared a few moments of darkness with such good company.
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 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 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.
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
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.
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.
On several of my wanderings these past few days, I have heard noticeable buzzing sounds that indicate an acceleration and flyby of a large winged insect. I recognize these sounds to be from a fascinating group, the robber flies, family Asilidae. I remembered posting about them last year and when I looked it up, it was almost exactly the same week last summer when I started seeing these amazing aerial predators in the yard.
Robber fly with honey bee prey (click photos to enlarge)
And, once again, the first one I saw with a prey item last week had managed to capture a honey bee. Their preference for bees is one reason this particular species is also called the false bee-killer (although not really so false).
Close up of a killer
A closer look reveals some of the adaptations that make robber flies so efficient at catching their prey, which, by the way, they almost always do while on the wing. They have huge eyes for spotting flying insects; large wings powered by strong muscles in the humped thorax; and long spiky legs that help them maintain a grip on something once they have grabbed it in mid-air.
Face to face with a fierce predator
This one did what they all do after catching something – flew to a perch to start consuming its prey shortly after capture. Robber flies pierce and inject their victims with toxins that immobilize the prey and begin to liquefy them. They then fly to a nearby perch and begin to imbibe on the internal soup of their quarry.
This time, however, the meal was interrupted. What had drawn me to this particular perched fly was an intense buzzing sound, not made by this fly, but by a male robber fly hovering nearby. The male had the distinctive white patch at the tail tip I had seen last summer that allowed me to identify them as Promachus bastardii, which Bug Guide calls the Big Robber. Turns out, this loud, stationary buzzing is a prelude to mating. And, sure enough, the male waited for just the right moment and then jumped on the larger, feeding female.
Mating robber flies
The act didn’t last long as I heard another buzzing sound and saw another male hovering nearby…the lady has two suitors. The first male buzzed off and the other male followed, so perhaps a territorial duel ensued elsewhere in the yard.
Female continued feeding
The female, meanwhile, continued feeding. That is, until I accidentally brushed her perch while trying to lean in closer for a better view. She immediately buzzed by my head, carrying her unfinished lunch to a less crowded perch. She will eventually lay eggs at the base of plant or in soft soil or rotting wood. The larvae are rarely seen, but resemble odd worm-like creatures living in soil and soft wood where they consume organic matter and start their predatory career by capturing soft-bodied prey around them. Larvae pupate in the soil and emerge next year, or perhaps a year or more later. I guess I will need to be on the lookout for some egg-laying behavior and see if I can’t find a larva. In the meantime, I’ll listen for that buzzing sound and see what’s for dinner.
It’s been a busy couple of weeks and I must apologize as I have been a blog-slacker I’m afraid. Lots of chores, plus the hot and humid weather has kept me inside more than usual. It turns out, unlike me, there are some things that actually do quite well in this sort of weather. The past few weeks have been wet and warm, perfect conditions for the many frogs here in the woods. And one place in the yard has been particularly popular.
Mini-pond awaiting repair (click photos to enlarge)
One of the two water gardens has a leak (or more than one) in the liner. I cleaned it out this spring but decided to put off attempting a repair or replacement of the liner until cooler weather next Fall. The heavy rains have partially filled this pool, making an ideal breeding ground for several species of amphibians, especially Cope’s gray tree frogs, Hylachrysoscelis. I have come home late on several rainy nights and their calls have been deafening. And where there are calling frogs, there are eventually eggs, tadpoles, and, finally, tiny frogs, or froglets.
Cope’s gray tree frog emerging from the pool
I started seeing these mini-frogs a couple of weeks ago, and their numbers have steadily increased, with plenty of tadpoles still active in the pool. When I look over the edge of the pool, I usually see 4 or 5 froglets sitting around the edge, most with part of their tadpole tail still present.
The tadpole tail slowly disappears after the frog leaves the water
As a tadpole changes into a frog, the cells in the tadpole tail undergo programmed cell death, called apoptosis (from a Greek word meaning “falling off”, as in leaves from a tree). This process is stimulated by thyroid hormones in the blood. This type of cell death differs from necrosis, where cells swell and burst, often due to injury, and spill their contents on neighboring cells causing an inflammatory response. Cells that undergo apoptosis die in a “neat” fashion, by shrinking and condensing, and are eventually consumed by other cells, thus recycling the organic components of the dead cell.
These mini-frogs could perch nicely on your thumbnail, with plenty of room to spare
It is amazing that all this intricate cellular processing is going on in these tiny creatures as they emerge and begin their terrestrial existence. Studies have shown that newly transformed frogs will stay close to the ground in vegetation, but will often migrate many feet away from their natal pool within a week or so. I am already finding froglets 30 feet or more away the pool. If even a small percentage of these guys survive, it will be a very noisy next summer on rainy nights here in the woods. Looking forward to it…
Here is a gallery of baby pics from the mini-frogs around the pool…
Roads End Naturalist 