Archive for the Parental care Category

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

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SHARPSHOOTERS AND BROCHOSOMES

Posted in Leafhoppers, Parental care, Predators/parasites/parasitoids with tags , , , on September 17, 2010 by Dr. Art Evans

By Arthur V. Evans

Broad-headed sharpshooter, Oncometopia orbona.

Sharpshooters (Oncometopia species) measure 11-13 mm in length and are among the largest of North America’s leafhoppers. They feed on a wide variety of plants growing in gardens, parks, meadows, and woodland edges during summer and fall. Their sap feeding activities may spread plant pathogens. Females use their knifelike ovipositors to insert eggs into soft stems. The eggs are covered with a chalky substance (egg brochosomes) that make them more resistant to excess moisture and protect them from fungal infections and possibly attacks by parasitoids.

Broad-headed sharpshooter with brochosomes.

Brochosomes are intricately shaped proteinaceous particles that are produced by kidney-like structures called Malpighian tubules and excreted as a solution. After the sharpshooter molts, the solution is spread over the exoskeleton as a water-proof coating. Female sharpshooters store brochosomes as a single white dot on each forewing to be used later as a protective coating for their eggs.

© 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

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

WOOD-EATING COCKROACHES INVADE VIRGINIA

Posted in Cockroaches, Darwin, Insects, Parental care, Virginia with tags , , , , on February 13, 2010 by Dr. Art Evans

By Arthur V. Evans

Just kidding. Wood-eating cockroaches have really been here in the Commonwealth all along. But they only eat really rotten wood, so they pose no threat to buildings or furniture. Let’s start at the beginning.

A few years ago, while conducting an insect survey in Shenandoah National Park, I pulled apart a very moist, rotten log to find several shiny black cockroaches over an inch long living in flattened tunnels apparently chewed out of the wood. With chunky, wingless bodies, and thick spiny legs, they resembled somewhat stunted versions of Madagascan hissing cockroaches, popular denizens of insect zoos and the occasional of pet shop.

I recognized these cockroaches immediately as the famous brown-hooded wood cockroach, a native species that has figured prominently in the scientific literature, especially over the last 10 years. Samuel Hubbard Scudder described Cryptocercus punctulatus in 1862 from a single specimen collected right here in Virginia. Draper Valley in Pulaski County, to be exact.

The brown-hooded wood cockroach, Cryptocercus punctulatus Scudder

Scudder was a noted authority not only of grasshoppers, cockroaches, and their relatives, but also of butterflies and fossil insects. He coined the term “Cryptocercus” from the Greek “krypto,” meaning to hide or conceal, and “kerkos,” or tail. This is in reference to the fact that the last three abdominal segments of Cryptocercus are hidden within a chamber created by the seventh abdominal segment.

Cryptocercus cockroaches are no ordinary cockroaches. They takes four to five years to reach maturity, mate for life, reproduce only once in their lifetime and only after they have lived as a couple for a year. Both sexes actively care for their young for up to three years. Most other cockroaches live only two or three years, are quite promiscuous, breed repeatedly, and never see their young, abandoning their eggs before they hatch.

Like termites, adult Cryptocercus chew meandering galleries in rotten logs of both coniferous and hardwood trees. The galleries consist of intersecting tunnels and arena-like chambers in which they raise their young. Females imbed egg cases, or oothecae, in the walls of the tunnels. The larvae, up to as many as 75 in a single brood, change from ivory or golden in color to progressively darker shades of reddish brown as they mature before eventually turning nearly black.

Both parents and offspring eat rotten wood and rely on bacterial and protozoan symbionts in their gut to help them metabolize their food; only termites and Cryptocerus cockroaches harbor these same specific gut symbionts. Since they come into this world without the necessary compliment of gut symbionts, Cryptocercus larvae must obtain them from special anal fluids produced by their parents, just like termites. Up to six cockroach larvae at a time will bury their heads deep within the anal chamber of an adult cockroach to suck up an elixir rich in life-giving bacteria and protozoa.

Young cockroaches grow by molting, or shedding their exoskeletons. As they molt, part of their intestinal lining is also shed, and along with it goes their gut symbionts. After each successful molt they must re-infect themselves by imbibing the anal fluids of their parents in order to metabolize wood and stay alive. By the time they reach their third or fourth larval stage, the young Cryptocercus no longer lose their gut symbionts with each molt and have become nutritionally independent of their parents. Also like termites.

Scientists have long thought that termites were offshoots of ancient cockroaches. Whether Cryptocercus cockroaches are “living fossils”  closely related to termites, or a more recently evolved line of cockroach that just happens to share an amazing number of features in common with termites is still hotly debated in the scientific literature.

Scientists eager to explore the interface of population genetics and environment, the key evolutionary forces that drive the development of new adaptations and speciation, find these cockroaches elegant research subjects. After all, they are dependent on a patchy resource (rotten logs), have limited powers of dispersal, and live in close-knit family units. Plus, whether they are primitive or not, the reproductive behavior of Cryptocercus mirrors that of a king and queen termite starting a new colony, which makes them the best living models for studying the development of social behavior in modern termites.

In the 1930’s two additional species of Cryptocercus were discovered in eastern Russia and western China. In 1997, comparative DNA analysis of populations in Appalachia and the Pacific Northwest produced results indicating that each population was actually a distinct species. A similar analysis of the Appalachian populations revealed a complex of four closely related species. One of the new species was named, predictably enough, after Charles Darwin (C. darwini), while another was named in honor of Jerry Garcia (C. garciai) of the Grateful Dead.

Since 1999, an additional five species have been found in East Asia, bringing the total number of species in the world to an even dozen. More species no doubt await discovery by scientists. From Draper Valley, Virginia to China, our understanding of Cryoptocercus and the light they might shed on the very dawn of termites continues to be a long, strange, yet very illuminating trip.

© 2010, A.V. Evans

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