The SWNP City-wide Nature Challenge
The late afternoon sun shone down over a wildflower-rich grassy clearing at the Southwest Nature Preserve in Arlington, between the gnarled, lichen-covered branches of post oak and blackjack, their trunks flanked by saw greenbrier that sprouted amid a carpet of fresh shoots of poison ivy. I was here for the city wide nature challenge, a day-long event in which citizens attempt to record the most species. It was a great opportunity to get out into the field, and to contribute some data as well.
The rays cast metallic jade shards of light off of the elytra of beetles zipping and darting about in a delicate rosy-white bed of evening primrose. They caught my eye, and I veered from the trail and knelt among the flowers to observe them. At this closer level I could identify them as far as the tribe Agrilini. These beetles emerge from the bark of various trees in late spring after spending many months as larvae, where they feasted on the fibrous tissue beneath the bark.
The buprestids weren’t the only invertebrates moving on this warm Saturday on the tail end of April. A rotund black and white scarab with dense golden setae was rolling around in the center of one of the primrose blossoms like a drunken bee. It was a Texas flower scarab (Trichiotinus texensis), a common species this time of year. It detected my presence and buzzed away on veined amber wings. The bright contrasting colors of black and yellow and white were suggestive of a bee or wasp, which the beetle mimics quite splendidly whether in flower or flight.
Another nearby insect also watched it go, somehow wise to its true identity, for had it been an actual bee the creature would have followed. This was a bee assassin (Apiomerus spissipes). In spite of its small size, it is a formidable predator, as its name suggests. Dressed in a mosaic pattern of maroon, yellow and dark brown that, when viewed from above, somewhat resembles a tribal face, it is well-concealed among the grasses and flowerheads. This is a member of the true bugs, and it is usually an ambush predator, perching in sunny patches in open areas, concealed amid the blooms of wildflowers as it waits for a visiting pollinator. The bug’s proboscis acts as a hypodermic needle, injecting a paralyzing venom that slows the victim’s movements before converting into a vacuum tube and sucking up its juices like a grim smoothie.
Eventually Michael and the group of contributors arrived, and we met with Nic Martinez at a pond near the front of the property. The goal was to drag a sein through the murky brown water in hopes of turning up some of its hidden aquatic denizens, but the mud was deep and thick, and it was instead decided that we dip from the shoreline with mesh nets intended for such purpose. In this manner we turned up robust, mud-mottled dragonfly and tuft-tailed damselfly naaids, as well as cricket frogs, tadpoles, and fairy shrimp. Behind us the newly emerged adult dragonflies tried out their new wings over the pond surface. One of them, a common whitetail, perched on a reed at water’s edge.
A flash of Halloween black and orange caught my eye, and I watched as a Monarch butterfly winged its way across the clearing, soaring over the top of an ashe juniper. If it were a female it was likely in search of a milkweed, the species’ host plant, where it could deposit its eggs. In a few weeks the sausage-shaped, tiger-striped larvae would be munching on the toxic leaves, absorbing the cardenolides and rendering themselves poisonous as well.
At the edge of the meadow I slipped into the realm of woodlands, where the sunlight fell in warm bright patches across my face. A Texas spiny lizard scurried around the trunk of an oak in their “barber pole fashion” up and around in a spiral, its hooked toe claws allowing it perfect vertical traction. In a moment it was out of sight.
Among the dried leaves and deadfall at my feet grew sugar hackberry trees with rough, wrinkled bark, stout post oaks with trunks the diameter of barrels, and blackjacks with their deep green, point-tipped leaves. The chaotic branches of gum bumelia could be seen like crops of untamed hair. A thick tendril of Virginia creeper slithered its way across the soil beneath, the characteristic quintet of serrated leaves standing out among tones of gray and sepia. In one place possumhaw grew at the base of a blackjack, and a little red weevil with a black snout sat perched on one of its leaves. This was Homeolabis analis, a beast who goes by the more colorful name of leaf-rolling weevil. They are small, generally around 6 mm in length, and are usually found in association with oaks, so the presence of this one beneath the blackjack was not surprising. Like the buprestids, adults pupate over the winter and emerge the following spring. In a complex process that is remarkably technical for such a tiny creature, the weevil picks a choice, soft leaf and measures it precisely, then selects a spot along the midrib, severing it to dam off the water supply to the leaf’s lower part. It then moves to the other side, where it repeats the process. After the leaf begins to wilt and lose strength the beetle notches the leaf on the bottom of the midrib,preparing it for a smooth, easy roll. The extending veins are then cross-cut in a determined, painstaking process where every cut is precise. The leaf is folded in half and then rolled. The female weevil then lays an egg or two in the center with her ovipositor and tucks in the flaps like a tortilla, to prevent unrolling (UF/IFAS).
Among the deadfall I found another nibbler of oaks, the ant-mimic longhorn beetle, Euderces pini. These are mimics of carpenter ants, and are similarly colored in bands of maroon and black. This, coupled by their comparative size, renders them quite inconspicuous among their armed lookalikes. As I watched a pair of them raced up and down the tangled, leafless branches of a severed post oak limb.
I had brought along a canvas beating sheet, sewn around a wire hoop in the form of a basket and suspended on a wooden pole to make a sort of “net.” With my free hand I gently rapped one of the branches of the overhanging oak, holding the basket as a catch-all beneath. The goal is to dislodge resting insects, which fall into the basket and can be observed, or, in this case, recorded for Inaturalist. This method works surprisingly well, and seldom fails to turn up a wide variety of insects and arachnids. On this day it would produce a little green stick insect, Diaphemorera femorata. The kings of mimicry,walkingsticks virtually disappear among the foliage of their choice.
When night fell the team of naturalists met up in the parking lot of the preserve and geared up for a night walk. We headed out across the edge of another large pond, where we saw fishing spiders performing little miracles on the surface of the water, their eight legs splayed out, sitting atop the thin membrane of molecules above the water. In the nearby reeds, long-jawed orbweavers climbed across the strands of their webs like acrobats. Our flashlight beams played across the water and mud, where Zev and I found a young plainbellied water snake that cut across the shallow edge like a black ribbon in the late twilight.
We traversed a small rocky hill, and in the middle of the sandy trail the beam picked up a black bug scurrying among the low grasses. This was a black corsair (Melanolestes picipes) another true bug related to the bee assassin that patrols the ground for crickets and small spiders. A bite from an assassin bug is incredibly painful, as I learned the hard way as a teenager, and can even leave the skin around the site of the bite numb for several hours.
Another member of the party discovered a striped bark scorpion (Centruroides vittatus), the only native scorpion species to occupy the western cross timbers. In spite of its inch-long size, it bared its pincers and arched its tail, the curved sting on the end of the telson at the ready. We admired its bravery and then saw it to the safety of the trail’s edge to resume its hunt for small arthropods.
We made our way through the woods, engaged in enjoyable conversations, and the night came to life all around us, with screech owls and chuck-wills-widows piercing the darkness with their pleasing calls. The night would end, but not before it had been thoroughly explored. Overhead the pale light of a waxing gibbous moon smiled over the preserve, a final witness to a memorable day at the Southwest Nature Preserve.
‘Beetles of Eastern North America’, Evans, Arthur V. Princeton Press, 2014