Archive for the Ants, bees, wasps Category

WHAT’S ALL THE BUZZ ABOUT NOBEL PRIZE SEASON?

Posted in Ants, bees, wasps with tags , , , on October 10, 2010 by Dr. Art Evans

By Arthur V. Evans

There have been plenty of reports in the news lately regarding the 2010 Nobel Prizes awarded for cultural and scientific endeavors. The prizes were established in 1895 in the will of the Swedish chemist Alfred Nobel, whose fortune was built on, among other things, the invention of dynamite. First awarded in 1901, the prizes are given annually in recognition of outstanding achievement in the fields of chemistry, literature, medicine, physiology or medicine, and physics. The best known and often controversial prize is the Nobel Peace Prize.

This is a good time to recall that nearly 40 years ago Austrian Karl von Frisch (1886-1982) received the Nobel Prize  in Physiology or Medicine in 1973, along with Nikolaas Tinbergen and Konrad Lorenz, for his pioneering work on communication between insects by studying the sensory perceptions of honey bees that led to the deciphering of their waggle dance in 1946. You can download a copy of von Frisch’s Nobel Lecture here.

Although sometimes claimed by entomologists as one of their own, Von Frisch was actually an ethologist, a zoologist that examines animal behavior relative to their environment. His studies with honey bees (Apis mellifera) produced several revelations. For example, von Frisch discovered that foraging bees were able to discriminate among different species by their scent and that individuals bees consistently forage among the same species of flower. He also learned that, in spite of a great sense of smell, the sense of taste is not particularly well-developed in bees.

He also established that bees can distinguish the colors of  blue, violet, white, and yellow, but that black and red were colorless and therefore indistinguishable to them. Under ultraviolet light, the pigments that make up these colors appear as multicolored patterns called nectar guides.

Von Frisch determined that bees orient themselves and can tell time of day primarily by their relative position to the sun. On overcast days or inside their hives, bees can still do all this by using the polarized light pattern of even a small patch of blue sky, or by relying the Earth’s magnetic field when moving about inside the hive, respectively.

Using all the tools at their disposal, Karl von Frisch proposed that not only do bees have the ability to gather orientation and temporal information from the sun’s daily movement across the sky, they can also relate this information to the current position of the sun from the dark recesses of the hive. This allows foraging bees returning from the field to provide up-to-date information on the direction and distance of nectar sources to their hive mates without having to go back outside to reorient themselves. This information is relayed by performing two basic kinds of “dances.” The information conveyed in these dances is received and interpreted on the vertical surface of the comb and put into practice on a horizontal landscape.

The round dance communicates information about nearby nectar sources about 50-100 meters from the hive. Whirling about in a tight circle, the dancing bee completes two circuits one way, then abruptly turns the other for two more circuits. Delivered on a thickly populated section of comb, bees in the immediate vicinity of the dancing bee struggle to keep their antennae in contact with the dancer’s abdomen. Soon the dancing bee’s wake is filled with bees all fervently trying to keep in step. Direction is not conveyed during the dance, but the type of flowers is transmitted through the dancing bee’s odor.

The waggle dance presents information on distant pollen and nectar sources. The dancing bee moves a specific distance in a straight line on the comb, turns and walks a half circle, then retraces the straight line and waggles its abdomen. Turning in the other direction, the bee completes a figure-8 pattern and waggles along the straight line again. The direction of the straight line relative to the vertical plane of the comb reveals the precise direction of food source relative to the position of the sun. The intensity of the dance, as measured by the number of times the waggle dance is performed informs the other bees as to distance of the food source. Bees receive and reinforce this information by copying the dance and by sensing the odors of dancing bee. Fully informed by the waggle dance, the newly recruited bees leave the hive and locate the food source regardless of intervening physical barriers, natural or man-made.

My first exposure to von Frisch and his groundbreaking work with honey bees was through the 1964 Life magazine article about his life and research at the tender young age of seven. Later in 1966, I saw him in one of the very first National Geographic television specials, The Hidden World of Insects (another milestone in this entomologist’s fascination with insects). I clearly remember being fascinated by his painstaking experiments with experimental feeding stations set among open grassy habitats and stocked with petri dishes of different colors and filled with various sugar solutions.

Karl von Frisch also studied the pheromones produced by queen honey bees and the role they had in maintaining the social order of the colony. Although he published all of his is original findings in German, von Frisch did produce some popular works in English. Two of these titles have long been in my library. Both works are fascinating to read. Animal Architecture covers both vertebrates and invertebrates, including some wonderfully illustrated information on the structures built by arthropods.

Scientists have long been skeptical or flat-out rejected von Frisch’s work with honey bees and his results suggesting that these industrious insects had a language all their own. Recent studies suggest that the importance of the bee’s dance may not be as great as once thought and that most of the bees that witness the dance get it all wrong, if they don’t just ignore it altogether. Only a few workers that “get” the information actually find the food source.

Other scientists are not ready just yet to discount the importance of dancing bees to the overall success of the hive. Both camps agree that most of the research thus far has focused on the message delivered by dancing bees and that there is still much to be learned how this information is perceived by other members of the hive.

WEB SOURCES:

2009. The bees’ knees-The facts. New Internationalist Magazine. http://www.newint.org/features/2009/09/01/facts-about-bees/ (accessed 10 October 2010)

2010. Karl von Frisch. Wikipedia. The Free Encyclopedia.  http://en.wikipedia.org/wiki/Karl_von_Frisch (accessed 10 October 2010)

PRINT SOURCES

von Frisch, K. 1953. The dancing bees. An account of the life and senses of the honey bee. New York: Harcourt, Brace & World Inc. 182 p.

von Frisch, K. 1974. Animal architecture. New York: Harcourt, Brace, Jovanovich. 306 p.

Williams, C. 2009. Show me the honey. New Scientist 203 (2726): 40-41.

COW KILLERS LACK THE VELVET TOUCH

Posted in Ants, bees, wasps, Defense, Insects, Parental care, Predators/parasites/parasitoids with tags , , , , on September 22, 2010 by Dr. Art Evans

By Arthur V. Evans

Velvet ants, some of which are also known as cow killers, are actually solitary wasps. The females are wingless and sting, while the stingless males are fully winged. Although incredibly painful, the sting is seldom dangerous. Velvet ants are rarely abundant enough to need any sort of control and are best left alone to go about their business.

Velvet ant diversity is greater in southwestern United States, less so in the Southeast. Although there are more than 40 species of velvet ants found in the Southeast, only one species in the region, Dasymutilla occidentalis, stands out. It is the largest species of velvet ant in North America and occurs from Connecticut to Florida, west to South Dakota and Texas.

In spite of its nickname “cow killer,” the stings of the female D. occidentalis are not fatal to cattle. The bold and contrasting colors of this velvet ant serves to warn predators that they are quite capable of defending themselves. They also make a squeaking sound by rubbing two abdominal plates across one another as an additional warning. The stingless male is automatically defended by its close resemblance to the female.

Lone females are often seen wandering about on the ground in open habitats from spring through late summer. Winged males patrol these same habitats for mates. Both males and females drink nectar for their nourishment. After mating, females begin searching for the ground nests of bumble bees. Upon finding a nest, the female velvet ant lays a single egg at the entrance of a bumble bee nest. The larva develops inside the nest as an external parasitoid on a bee grub; pupation occurs in the bumble bee’s nest.

Resource: Evans, A.V. 2007. National Wildlife Federation Field Guide to Insects and Spiders of North America. NY: Sterling. 497 pp.

© 2010, A.V. Evans

TARANTULA VS. TARANTULA HAWK

Posted in Ants, bees, wasps, Arachnids, Arizona, Insects, Parental care, Predators/parasites/parasitoids with tags , , , on September 15, 2010 by Dr. Art Evans

By Arthur V. Evans

One of nature’s classic battles is that of the lopsided struggle between a tarantula and its arch nemesis, the tarantula hawk (PepsisHemipepsis). I say lopsided because the odds are usually stacked against the tarantula. The arachnid, paralyzed by the wasp’s sting, is destined to be dragged off and stuffed down a previously dug burrow to become an egg-laying site and eventual fodder for a ravenous wasp grub.

In August, I photographed a tarantula hawk as it dragged a paralyzed female desert blonde tarantula, Aphonopelma chalcodes, across a coarsely gravelled driveway at the foot of the Huachuca Mountains in Sierra Vista, Arizona.

I first became aware of this saga in Walt Disney’s Academy Award winning documentary The Living Desert (1953 and later re-released in 1971) that depicted a day in the life of desert flora and fauna and the struggles of the latter to simultaneously find food and avoid being eaten themselves. It was 10 minutes of film footage featuring a tarantula hawk grappling with a tarantula shot by N. Paul Kenworthy, then a doctoral student at UCLA, that inspired Disney to produce his first documentary. Kenworthy later became one of the two macro cinematographers on the project. I met The Living Desert’s other macro cinematographer, entomologist Bob Crandall, while I was in high school. But that is another story for another time.

© 2010, A.V. Evans

A TALE OF PREDATOR AND PREY

Posted in Ants, bees, wasps, Arachnids, Predators/parasites/parasitoids, Spiders with tags , , , , on May 4, 2010 by Dr. Art Evans

By Arthur V. Evans

I had just spent a grueling three hours in the sweltering afternoon heat stalking insects and spiders with my camera along the James River. As I walked through the gate toward the parking lot at Reedy Creek, I saw a spider wasp with shiny dark wings flitting about agitatedly in the road. With another dozen or so exposures left in my camera, I decided to get a few pictures of the wasp before calling it a day. She flew all around me, landing briefly here and there before taking wing again. My patience quickly wore thin in the heat and I decided that enough was enough. But then I saw what had kept the wasp in the vicinity.

Lying perfectly still and in pristine condition was a wolf spider splayed out in the middle of the road. It had been laid low by the paralyzing sting of the spider wasp and was destined to be hauled off and stuffed down a nearby burrow to become fodder for a wasp larva. I decided to stake out the living corpse right then and there in the middle of the road. Sprawled out in the rapidly fading sun I aimed my camera at its still body in anticipation of photographing the predator with its prey.

For nearly ten minutes the wasp flew circles around me, frequently landing and running over the ground to search in vain for the hapless arachnid. At first I thought she was intimidated by my presence, but several times the wasp came within inches of me and my camera. Time seemed to drag on as the wasp inspected every piece of real estate in the immediate vicinity, except the tiny parcel that actually had the spider.

The occasional cyclist or jogger went past, but no one stopped to ask what I was doing. Then I heard the slow crunching of gravel coming toward me along the railroad tracks. A Richmond police car slowly wheeled toward me and stopped about 50 feet away. From my perspective down on the ground the car’s headlights seemed to stare at me like two giant bug eyes separated by shiny and toothed mandibles.

I smiled in the direction of the officer and wondered what he must be thinking. Just then a big panel truck hauling a trailer load of bright blue kayaks pulled up beside me. I looked up as the driver inquired if I was all right. I assured her that I was just fine and that I was waiting to take a picture of a wasp attacking a spider. She said she hated spiders and hoped the spider would meet its demise and then drove off to deliver her cargo by the river.

Then the police car pulled up. The officer told me that he did not want to ruin my shot and had decided to wait. But then he figured that if the kayak truck hadn’t spoiled my shot, his police cruiser probably wouldn’t either.

With all the hubbub I thought for sure that the wasp would have been scared off, but it was still scouring the ground in search of the spider. Finally it ran right up to the spider and inspected it nervously with its curled antennae. Suddenly it grabbed the spider’s leg with its mandibles and began to drag it away with surprising speed across the open ground.

Just as the wasp and spider cleared the roadway a thundering herd of about 40 young kayakers and their river guides stampeded over the site where I has just spent the past three-quarters of an hour on wasp watch. I paid them little attention as I crouched and crabbed along the access road paralleling the railroad tracks, following the wasp’s progress through my lens.

Every now and again the wasp would abandon the spider, apparently wandering off to reconnoiter the next leg of its journey. After a few minutes I could see the wasp negotiating its way back through the tangled growth.  As before, the wasp briefly inspected the spider with its antennae before grabbing a leg with its mouth and setting off on a new course.

The sunlight was beginning to fade when the spider wasp ditched her booty once again. I had two more shots left and decided to wait for the wasp to return one more time. I waited another 10 minutes or so for the wasp to come back, but it never did. I decided to call it a day and could only assume that the wasp was out somewhere, simultaneously excavating a spider’s grave and preparing a wasp’s nursery.

Excerpt from “What’s Bugging You? A Fond Look at the Animals We Love to Hate, University of Virginia Press. © 2008, A.V. Evans

CARPENTER BEES ARE BORING!

Posted in Ants, bees, wasps, Insects, Parental care, Pests with tags , , , , on April 1, 2010 by Dr. Art Evans

By Arthur V. Evans

It's spring and the eastern carpenter bees, Xylocopa virginica, are back!

The usual suspects of spring are all around me once again, including large, buzzing, blue-black eastern carpenter bees, Xylocopa virginica. They are noisily patrolling dead limbs and wooden structures in our neighborhood as they search for mates and nesting sites. Unlike the social honey bee imported from Europe, carpenter bees are solitary creatures native to North America. The bees buzzing around now reached maturity last summer. Back then they stretched their wings for a bit before tucking themselves away for the winter deep within the recesses in the very nest chamber where they had grown up.

Unlike the dark-faced female, the male Xylocopa virginica has a white "face."

White-faced and stingless, males are very territorial and spend much of their time claiming prominent flowering plants and bare patches of ground as their own. They aggressively drive off other bees and insects and often face-off with unsuspecting humans that unwittingly venture into their territory. The territorial borders of male carpenter bees are quite fluid and change from day-to-day. Amorous males regularly patrol flowers in search of females. Courtship involves lots of loud buzzing and aerial acrobatics, with the pair flying apart and coming together several times.

Dark-faced females are capable of delivering a painful sting, but are relatively docile. They chew their nest tunnels in dead trees, logs, or unfinished wooden structures, especially those with southern or eastern exposures. Females will consider exposed rafters, old house frames, picnic tables, rail fences, posts, trellises, and other exposed wood surfaces as potential nest sites.

With their powerful jaws working non-stop day and night, female carpenter bees will chew a perfectly round entrance hole that is about one half-inch in diameter. After tunneling in about one body-length, the tunnel turns sharply to the left or right at a 90º angle to follow the timber’s grain. They may construct two or more parallel tunnels from the main entrance that measure up to 14 inches long, each slightly wider than the entrance in diameter.

Sometime in May or June, the first egg is laid on a doughy pill of pollen about the thickness of a kidney bean at the end of a blind tunnel. The provision of pollen serves as the sole food source for the developing bee grub. The surrounding wood in the tunnel is then chewed into a fine pulp for form a disk-shaped partition that seals the egg off in its own cell. Each tunnel may have up to 6-8 cells.

Carpenter bees do not eat wood, but rely instead on flowers for nourishment. As the adults forage for pollen and nectar, they will mark each flower that they visit with a repellant chemical, or pheromone, that lasts up to 10 minutes. By skipping marked flowers carpenter bees can save time and effort by avoiding flowers recently depleted of their resources by other carpenter bees.

Tolerance is the key to appreciating carpenter bees. In spite of all the sawdust created by their nesting activities, they seldom cause severe damage. What damage they do cause is easily offset by their pollination services. Our gardens, fields, orchards, and forests would not be nearly as productive if it were not for their efforts and those of other pollinators. Besides, whether they are energetically visiting flowers, zooming through the air in conjugal bliss, or tirelessly engaged in nest-building, carpenter bees are just darned fascinating animals to watch!

© 2010, A.V. Evans

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