Beneath the Bark

Sunday afternoon saw Michael, Zev and I ascending a sandy trail up from the black water and dense vegetation of a section of bottomland forest at the Gus Engeling Wildlife Management Area in Anderson County, Texas. It was a warm day (warm for mid-February at least) with the temperature hanging just under the sixty degree mark. While Michael is no stranger to the area, I had only visited once on a very brief side trip on the way back from the Big Thicket, which lies about 150 miles to the southeast. Zev had never been at all, and all three of us were excited to see what natural treasures the day had in store. After four months of cold it was nice to be out in the forest during this brief warm spell. Zev was hoping to see an eastern newt, and Michael was adamant about exploring the post oak savannah. I, however, had bugs on the brain as usual. After all, conditions were perfect for finding a plethora of overwintering species in choice microhabitat that just so happened to be all around us. It didn’t take much searching to find what I was looking for. A massive post oak stood tall and straight at the edge of a tannin-rich pool, its leafless black limbs reaching for the sky. In truth it was not unlike so many other oaks growing all around it, except for one little difference. The bark around the lower trunk was raised slightly, separated from the tree by a shadowy space where I knew a mystery grab-bag of invertebrates potentially lay in wait. I stepped to the side of the trail and gently peeled it back, trying to be mindful that this was many creatures’ home and therefore trying to keep the destruction at a minimum. As I pulled the bark, separating it from the base of the trunk, I was rewarded by a fine sight: a female southern black widow spider had constructed her infamous messy web here, where she now sat with her scarlet hourglass pointed at me, the globular ebony abdomen shining like a black marble. Around her, a quartet of tiny beige and black marked fungus beetles sat, waiting out the winter months on a bed of spongy white granular fungi that was smeared across the wood like paste. I snapped a photo as Michael ventured over to see what I had found. Afterwards I replaced the bark as closely to its original state as I could get, and we continued making our way upland.

A black widow (Latrodectus mactans) and fungus beetles (Ischyrus quadripunctatus) beneath bark

While winter is a time when many insect species see an end to their life cycles after the first freeze, and most of our lepidoptera are tucked away safely in their insulated cocoons, there are many species which ride out the long harsh days of ice and sleet beneath a thick layer of tree bark, where they enter a torpid state of dormancy until the call of spring ushers them back to life.  Some can be found communally, huddled together in odd clusters, while others tend to be found singly. From centipedes and millipedes to spiders, beetles, true bugs, ants and wasps, a little peek beneath the bark on a winter walk in the woods is sure to eventually provide one with a behind-the-scenes look at how arthropods (and even some vertebrates) spend their winter vacation.

A ripe stump in the Trinity River bottomland, awaiting exploration

We continued along the trail, where a prescribed burn had cleared away much of the undergrowth and allowed us easy access to the post oak savannah. Here, the charred black remnants of timber littered the sandy, nitrogen-rich soil. Bone-white tree trunks, their bases scorched and bark peeled back like finely shaved coconut slivers, were full of promise. Sure enough, we found not only invertebrates but a couple of slumbering prairie lizards in this area, and Zev learned about the bright turquoise patches on the undersides of the males of this species that can be used as a differentiation key between the sexes.

Fires, while generally considered to be destructive from our human perspective, are beneficial to ecosystems such as pine forests and grasslands, as they burn away sections of old growth and overgrown thicket so that new plants can start over in their place. The ashes of the burned wood that mix in with the soil are high in nitrogen and contribute to the nutritional medium the new plants spring up in. Without periodic fires (either caused naturally by such factors as lightning strike or intentionally set and maintained by the forest service) our forests and prairies would quickly be overtaken by brush and invasive grasses.

Michael & Zev walk the trail to a burned section of post oak savannah

After exploring the burned section of fringe habitat for a while, we moved even further upland, where a wide looping trail was bordered by a barbed wire fence. Here the brush had been cut back extensively, leaving a generous amount of deadfall in the wake of the dozer. We all began turning over choice logs and sheets of bark, and in doing so located a number of interesting creatures. The first was a southern yellowjacket queen, tucked neatly away in a crevice under a spongy section of oak. What many people call “yellow-jackets” are in reality paper wasps, a large genus of vespids collectively grouped under the name Polistes, whose familiar water-resistant nests constructed from plant fibers mixed with saliva are seen hanging from porch eaves and barn rafters. The real yellowjacket is smaller and nests underground, building a roughly rounded structure the size of a basketball. Yellowjackets are generally more aggressive than paper wasps, although this dormant queen seemed too snug and content to worry about us as she sat patiently awaiting the first warm days, whereupon she would set out to begin a new colony. It is for this reason solitary yellowjacket queens are known as “foundresses”.  Looking down at this one it was hard to believe she held the potential to build an empire of soldiers that, over the course of a few seasons, could expand to 100,000 or more individuals.

Foundress of a vast future empire: Southern yellowjacket queen

Polypleurus perforatus, a strange tenebrionid with densely punctate elytra

The trail eventually led back around to another section of open, sandy savannah, with post oaks and hackberries growing spaciously over some type of rough, woody growth that resisted the progress of our boots, forcing us to plow through it with some difficulty. Saw palmettos and patches of azalea mixed with greenbrier further inhibited our travel across this landscape. A small grove of oaks, their lower trunks showing signs of peeled, aging bark, beckoned to me from the trail, so I braved the undergrowth and walked out into the field to give them a look. Although it took a bit of time, the effort was well worth it, for this proved to be a popular brumation spot for inverts. The dried hull of a metallic wood-boring beetle of the genus Polycesta was found beneath the first sheet of bark, its head and abdomen missing but elytra and thorax still present, a relict of chitinous armor that spoke of the past summer, of a creature that had at one time possessed a set of mandibles powerful enough to chew through the heartwood of the oak but had now been reduced to minute bits of ant food. Still, the sculptured pitted elytral pattern gleamed in the late afternoon sun like pyrite, a testament to the profound beauty and intricacy of these remarkable insects.

Stand of young pines on the border between savannah & woodland, Gus Engeling

Not far away from it sat a huge assassin bug, Microtomus luctuosus, a tricolored beauty that is kin to the dreaded kissing bug, a vector for the potentially debilitating Chagas disease. Also known as American trypanosomiasis, it is caused by the parasite Trypanosoma cruzi, and is transmitted to humans through the feces of the insect, which are involuntarily rubbed into the bite wound when the victim scratches the skin around the site of the bite. Chagas is a serious threat, especially in Texas, where a study conducted by Texas A & M found as many as half of the population of kissing bugs in the state to be carriers. Chronic complications from the disease include intestinal damage, heart problems, and can even lead to cardiac arrest in extreme cases.

Fortunately this was not the dreaded kissing bug (Triatoma sp), which also makes its home beneath tree bark, but a much more welcome and colorful member of the family. While it is larger than the kissing bug and capable of delivering a painful bite should one be so inclined to handle it carelessly, it carries no known communicable diseases. The species enjoys a wide range from central Texas south as far as Panama, where it is attracted to lights and feeds exclusively on smaller invertebrates.

Microtomus luctuosus

From the post oak savannah we followed the trail back downhill, where it led to a small pine grove flanked on all sides by water elm and sweetgum trees. Gradually we descended back into bottomland forest, and the rich earthy smells of organic mud could be detected on the breeze as we left the openness of the plain for the shadowy realm of the trees. In little time my eyes fell upon a dying pine. Unlike oak bark, pine bark tends to slough off in huge sections, and as I pulled the bark on this one back I couldn’t help but be reminded of a morning on the Louisiana border when I pulled off a great sheet of bark that broke off six feet above my head and rained an overwintering colony of imported red fire ants down on me. That had not been a serendipitous morning, but this pine tree would offer much better rewards beneath its flaky exterior. A small group of rough shield bugs (genus Brochypelma) were huddled up beside a few of the strangely rotund smaller shield bug Lineostethus sp.  Close beside them sat a cryptically marked click beetle, and several examples of the dull black tenebrionid, Alobates pensylvanica.  It was a true insect menagerie, a communal late winter gathering of mini-beasts, and a treasure trove of photographic potential for a student of entomology.

Shield bugs beneath pine bark

Click beetle

From the pine grove the trail wound back around to the vehicle, which was parked beside a bridge overlooking a small creek. From there we drove to a large section of bottomland where most of the forest floor lay beneath a shallow lake of dark water. At first glance the place looked as if a bulldozer had run amok through the woods, but upon closer inspection it proved to be the work of feral hogs. Feral hogs are notorious for working their way through patches of habitat, rooting and ripping and tilling up the ground and gobbling up everything they come across, leaving a trail of razed devastation in their wake. It did make for easy walking though.  The bottomland was replete with rotten logs and deadfall, and as we made our way along I knew it would only be a matter of time before I ran into more invertebrates.

Hemiscolopendra marginata

Solopocryptops sexspinosus

While Michael and Zev walked the edge of the waterline, with Michael photographing a basking redeared slider and Zev exhibiting his climbing skills across a felled tree, I resumed my pace, flipping and peeling bark, knowing that our time here was running short as the sun fell back over the treetops to the west. I found several centipedes here, as well as a handful of wolf spiders of the genus Hogna, and a pair of bess beetles as well. Also known as the horned passalus or patent leather beetle, this remarkable species is one of the few recorded types of beetles that rears its young. Bess beetles live in the pithy center of rotting logs and stumps, where they exist in communal family groups, with new generations growing up and “joining the family” to care for the next season’s progeny. They communicate through stridulation, whereupon they rub their wings against a special structure located on the underside of their wing covers, producing a high-pitched squeaking sound. While many species of insects are capable of producing sound in this way, bess beetles are unique in that their larvae “squeak” back by rubbing their legs together, demanding food like nestling birds. Bess beetles are important contributors to the breakdown of decaying wood in the forest, and their presence is generally indicative of a healthy ecosystem.

Bess beetle, in situ

From there we traveled upland, with no sign of Zev’s newts in spite of what felt like a thousand logs turned. “You’re not trying hard enough”, was his response when I asked him why he thought we weren’t seeing any.  “Dad has a metal ankle and a bad back”, I said. “Maybe they can’t be found because they’re good at not being found. That ensures their survival”.  But Zev would hear none of it.

At the day’s end Michael drove us up to another section of post oak savannah, and we tried out a trail that seemed to lead endlessly into dried bluestem sparsely dotted with small oaks.  As soon as we got out of the car I turned an oak log and found a pretty little black and white weevil that popped its head out from between the bark layers. It was Euparius lugubris, a first recorded sighting for Inaturalist.

Euparius lugubris

It had been a wonderful day of relaxation, an honorable day of rest. Aside from a throbbing back from rolling too many logs, I was glad to be back out into the field at the tail end of winter. As the air cooled and the sky darkened we said goodbye to the Gus Engeling Wildlife Management Area with plans for future trips already bouncing around in our conversation. It was back to the warmth of central heating to see me through until winter’s end.  We pulled back out onto the highway and headed for home, with the dense oak and pine rich forest all around us. Thousands of trees supporting a vast array of life through the winter, beneath the bark.

Bottomlands, Gus Engeling WMA
Kaufman Field Guide to Insects of North America: Eaton, Eric R & Kaufman, Kenn; Houghton-Miflin Harcourt; 2007

Whats biting texas? The hidden threat of Chagas disease”, Jennifer R. Hericks, 26 Jan 2016; The Houston Chronicle

Kissing bugs and chagas disease in the united states;; agriculture and life sciences, tx a&m university

Beetles of Eastern North America; Evans, Arthur V; Princeton University Press; 2014

Recyclers in the Circle of Life: Bess Beetles; Michael J Raupp;

Observations on the life history of the horned passalus: LE Gray, 1946

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