Archive for Ants, bees, wasps

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

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

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