Archive for the Aquatic Category

BELLY UP TO THE GRAVEL BAR FOR TOAD BUGS

Posted in Aquatic, Defense, Insects, Predators/parasites/parasitoids, True bugs, Virginia, Virginia State Parks with tags , , , , on March 28, 2010 by Dr. Art Evans

By Arthur V. Evans

One of my favorite haunts for insect photography is a small and unassuming gravel bar located just downstream from the dam that keeps the Swift Creek Lake within its banks in Pocahontas State Park, Virginia.

The toad bug, Gelastocoris oculatus, is widely distributed throughout southern Canada and most of the United States.

Gravel bars are tough places to live. Their surfaces can reach blistering temperatures or be completely inundated by flooding waters. Still, they support insects adapted to live under such harsh conditions that are seldom found anywhere else.

Many larger species spend their days hiding under stones and their nights foraging for food and mates. Some smaller species spend their entire lives comfortably wedged between the narrow, wet spaces between pebbles and coarse grains of sand. And still others are just passing through.

Not long ago, with a rushing stream at my back, I slowly knelt down on thankfully padded knees to recalibrate my focus on this universe wrought small. It took me of bit of time and patience to get my head out of the hustle and bustle of modern-day life, shake off the city with its noise and congestion, and begin to really see and appreciate the tiny inhabitants of this rocky shoal.

Bit by bit I took in my surroundings. Suddenly, a bit of movement drew my eyes toward a small embankment. I kept staring at the spot as I inched toward it, hoping to see whatever it was moving again. But it didn’t. Then it did, and I zeroed in on the spot. Just as the short, warty bug with bulging eyes came into focus, it jumped away. It was a toad bug, Gelastocoris oculatus.

It was as if I had just seen an old friend. I can still remember my very first encounter with this species along the edges of Little Rock Creek that meandered slowly out of the San Gabriel Mountains to the southern fringes of the Mojave Desert in Southern California. This species of toad bug is widely distributed throughout southern Canada and most of the United States.

The rough bodies of toad bugs are usually dull and mottled with brown and black. The base colors range from almost entirely yellowish, reddish-yellow, grayish-black, to nearly black. As a result, toad bugs are masters of the disappearing act.

Their front legs resemble those of a praying mantis, only shorter and chunkier. And like praying mantises, toad bugs are voracious predators and use these legs to capture small insects.

In Virginia, both larvae and adults live gregariously in a variety of habitats along the muddy, sandy, or gravelly margins of ponds, streams, and rivers. Overwintering adults appear in spring to feed and mate.

From May through September each female lays a dozen or so white eggs at a time in the sand, probably 200 or more in their lifetime. The eggs hatch in about two weeks; another two or three months are required before the larvae reach adulthood.

The toad bug eventually abandoned the gravel bar and disappeared into some low herbaceous growth nearby. I turned to find a small coppery ground beetle with bulging eyes, bright green legs, and patches of purple on its back running across the gravel, but this is a story for another time.

© 2010, A.V. Evans

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OUR SEAS OF PLASTIC

Posted in Aquatic, Education, Environment, Musings on March 30, 2009 by Dr. Art Evans

I want to bring to your attention the efforts of a former colleague of mine at the Natural History Museum of Los Angeles County, Dr. Marcus Eriksen. Marcus is a man of many talents: scientist, educator, author, conservationist, and adventurer. As the Director of Research and Education at the Algalita Marine Research Foundation , he is actively involved in the protection of marine watersheds through research, education, and restoration. Marcus and the AMRF team are at the forefront of studying the massive accumulation of plastic debris in our oceans and the impact of this pollution on marine life and the human food supply. Hundreds of millions of tons of bottles, bottle caps, cigarette lighters, bags, food containers, toys and other plastic items are washed through our watersheds and into our oceans each year.

Phase I of this AMRF study, dubbed “Message in a Bottle,” began with a research voyage into the North Pacific Gyre to investigate plastic pollution that has been dubbed the “Great Pacific Garbage Patch.” In Phase II, Marcus and a colleague sailed 2,600 miles from Los Angeles to Hawaii last summer on a raft made from 15,000 plastic bottles to raise awareness of plastic marine debris fouling our oceans.

Phase III begins on Saturday, 4 April when Marcus and his fiance Anna ride their bicycles 2000 miles from Vancouver, British Columbia to Tijuana, Mexico. Along this route they will distribute samples of plastic debris collected from the North Pacific Gyre to legislators, educators, and organizations to raise awareness of plastic debris in our oceans.

The problem is that plastic is designed to last forever, yet we use it regularly to make products that are thrown away. Although recycling is effective for paper, metal, glass, and other materials, it is not the answer for plastics. And as a petroleum product plastic, like our consumption of gasoline, keeps us dependent upon foreign sources of oil.

The “Message in a Bottle” project has encouraged me to rethink how I use plastic products at home and in the workplace. My first small step into this brave new world is to avoid purchasing or using drinks of any kind in plastic bottles, especially water. Then I am going to try to encourage my favorite take-out eateries to start using more eco-friendly to-go containers. A recent trip to the grocery store was sober reminder of just how pervasive plastic is in our culture, but there are lots of creative people out there who are coming up with practical and interesting ways for reusing and recycling these containers.

If we all do our part, and encourage our colleagues, clients, and visitors to do the same, we can make a difference and help to reduce the amount of plastic debris that finds its way into our oceans!

OUT WITH THE NIGHT SHIFT

Posted in Aquatic, Beetles, Defense, Insects with tags , , on February 9, 2009 by Dr. Art Evans

It’s late afternoon. The air is hot and thick, draped like a hazy, wet blanket over the landscape. The dull orange sun hangs heavy over the tops of trees lining the lake and soon drops out of sight. Whirligig beetles drift lazily in the placid water, barely leaving a ripple in their wake. Dragonflies dart back and forth, gobbling up their final meals of midges and other tiny flying insects for the day.

As dusk approaches the throbbing wail of cicadas loses its urgency and eventually stops, as do the relentless attacks of blood-sucking deer flies. The white-throated swifts that had ruled the skies for most of the afternoon are now settled in for the night, giving way to their mammalian counterparts, the bats. Several of these amazing animals skim the lake’s surface right in front of me to drink.

I am in the vicinity of Group Camp 7 in the southernmost reaches of Pocahontas State Park. Accessible only on foot or by horseback, this sylvan oasis within the park definitely has a feel of remoteness seldom experienced so close to a major metropolitan area.

With more than 7,600 acres, Pocahontas is the largest state park in Virginia. Located just 20 miles southwest of downtown Richmond, the park is probably best known for its swimming pool, camping and conference facilities, outdoor performances, and music festivals. But it is also a favorite haunt among local naturalists, especially birders. I have visited the park regularly for the past five years to observe and photograph Virginia insect life during the spring and summer.

As the day shift winds down, the creatures of the night slowly begin to stir, gearing up to take their place on the evening stage. With the arrival of twilight there seems to be a moment or two when all insect life seems to pause briefly, and then the night shift takes over.

The twinkling lights of amorous fireflies begin to appear about the low growth sprinkled along the woodland floor. Neither bugs, nor flies, these soft-bodied insects are actually beetles. Males engage in a slow, looping flight with repeated dips to create a J-pattern with their lights. At the bottom of the descent their abdomen glows bright yellowish-green, becoming dimmer before shutting off completely at the top of their ascent. Their oversized compound eyes are trained on the not-so-distant darkness, hoping to see the light of a female responding with her own perfectly timed and pulsating response amidst the low, herbaceous growth.

Later in the evening another species appears, flying high and fast in the canopy, releasing its light in rapid bursts of three. Fireflies have developed this system of luminous Morse code to locate mates of their own kind among the tangled growth and avoid fruitless encounters with the wrong species.

Chunky June beetles begin to rustle, slowly rising through the air from their daytime hiding places amongst the leaf litter with a buzz. They plow through the night air as if they were trucks in low gear, slowly gaining speed as they begin their nightly search for mates and fresh leaves to eat .

With a headlamp strapped to my sweaty forehead, I venture forth like a bright-eyed Cyclops in search of more of the Commonwealth’s nocturnal insect and spider fauna. The forest floor seems to glitter with tiny stars, which turn out to be the tiny, unblinking eyes of wolf spiders reflecting the beam of my light. They too are searching for insects.

As my headlamp cuts through the ever-growing darkness, moths, beetles, and other airborne insects fly in and out of the sharp beam. Some plummet into my face as they try to reach the light’s source.

For years entomologists have taken advantage of the fact that many insects are attracted to lights at night. Using the ultraviolet component of distant light to orient themselves, many insects are uncontrollably drawn to nearby artificial lights, such as flickering campfires, hissing gas lanterns, brightly lit store fronts, and streetlights. Not the sad, dull yellowish lights that inhabit city streets, but the bright, inviting glow of mercury vapor lights that dot the lesser populated areas of the state.

Lights strong in the ultraviolet spectrum are especially attractive to nocturnal insects. I use several BL black lights specifically for attracting night flying insects. Set in front of and above white sheets for reflectivity and contrast, and powered with 12-volt gel cell battery, the eerie purple glow works like a bug zapper, but without the zap.

Warm, humid, moonless or overcast skies seem to be the best nights to “black light” for insects since there is less ultraviolet light to compete with my set up. The greatest insect activity at lights is right after dark, between 9:30 and 11:00 PM, although some of the larger beetles and moths seldom make an appearance before midnight.

Nocturnal insects can easily maintain a steady flight path in relations to distant sources of light. However, they must fly in ever-tighter spirals in order to maintain their orientation to a nearby light source. Eventually they alight on the sheet or nearby vegetation. If left undisturbed, most would remain within sight of the light until dawn when the rising sun would drive them to seek shelter from the heat and hungry birds.

As night falls, insects swirl about my black light like small comets. My sheet was soon covered in a dizzying array of insects ranging from tiny gnats and beetles just millimeters long, to relatively giant mayflies and June beetles. Dozens of plump, fuzzy moths of all colors settled on the sheet like fighter planes on a flat top. Shiny, smooth and streamlined aquatic beetles emerged from the nearby lake and clambered awkwardly beneath the light, like proverbial fish out of water. Perhaps 200 different species of insects in all made an appearance at the light. The preparation and identification of this relatively small showing would require the full-time efforts of an entomologist for at least a year.

Occasionally a bat hurtled through the cloud of insects, gobbling them up as if they were bellying up to an airborne buffet. Using a series of high-pitched clicks like radar to locate airborne insects, the bats dart and bank sharply through the night air in pursuit of hapless insects.

But not all insects are defenseless against bats. Some moths and mantids have special “ears” capable of picking up signals bats use for their echolocation system. Upon hearing the call of a nearby bat, these insects will take sudden evasive action by pulling in their wings and dropping to the ground or making a spiral power dive to safety.

After 11:00 PM the waves of incoming insects began to slow to a mere trickle. I packed up just after midnight, but the choruses of frogs, katydids, and crickets continued to rise and fall. Although I am sure that they sound like a raucous cacophony to many, I found the chirps, clicks, buzzes, twangs, and bellows to be joyous noise, a perfect sound track for an evening out with the night shift.

©2004, Arthur V. Evans

WINTER STONEFLIES

Posted in Aquatic, Stoneflies, Winter with tags , , on February 4, 2009 by Dr. Art Evans

In Virginia, one of the very first insects to make an appearance in the New Year is the winter stonefly, Taeniopteryx. These flat, slender, and sprawling insects are grayish brown and measure 9.0 to 11.0 mm in length. They are also known by other appellations, such as willowflies and early black stoneflies.

Most of their lives are spent as larvae that nibble on aquatic vegetation and submerged debris as they crawl along coarsely pebbled and rocky bottoms of large streams and rivers. Beginning in late January or early February, the mature larvae leave their watery past behind for good and haul themselves up on nearby rocks and vegetation. The freshly emerged adults, having just escaped their larval exoskeletons, soon festoon boulders, logs, bridges, and nearby buildings by the dozens, even hundreds. They are most evident on warmer days, but are seldom noticed by passersby, save for naturalists on the lookout for signs of life after a long winter or anglers reading the latest hatch.

img_9991For me, the sudden appearance of these hardy insects serves as an annual reminder that winter is almost over and spring is on the way. This is welcome news to entomophiles living in the frosty and leafless eastern United States!

Many thanks to Boris Kondratieff of Colorado State University for helping me with the intricacies of winter stonefly identification.

©2009, A.V. Evans

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