Archive for Orthoptera

GRASSHOPPER LOVE

Posted in Arizona, Defense, Grasshoppers & crickets, Insects with tags , , , , , on September 15, 2010 by Dr. Art Evans

By Arthur V. Evans

Arguably the most spectacular looking and certainly among the most distinctive of all the grasshoppers in North America, painted grasshoppers, Dactylotum bicolor (24-32 mm) are a riot of color. These boldly marked orthopterans are also known as rainbow or barber-pole grasshoppers. Studies have shown that diurnal predators, especially birds, will avoid eating them presumably because of their aposematic coloration. Females tend to be significantly larger than the males.

Painted grasshoppers make their living along the western edge of the Great Plains from southern Saskatchewan south to western Texas and northern Mexico, and west to Arizona. Active from mid- to late summer, painted grasshoppers feed on a wide variety of desert plants, especially grasses and low broadleaf plants.

© 2010, A.V. Evans

WHAT’S IN YOUR BASEMENT?

Posted in Environment, Grasshoppers & crickets, Insects with tags , , on March 9, 2010 by Dr. Art Evans

By Arthur V. Evans

While moving some bags of potting soil on the front porch a few years back, I discovered a gathering of variously sized leggy and very nervous creatures. Their pale bodies, not quite reaching an inch in length, appeared to be brown banded, supported by long legs mottled with patches of gray and rust. Their long, hair-like antennae waved nervously about as I knelt down for a closer look. At first glance, they looked decidedly spidery in appearance. They scampered easily up, over, and around vertical surfaces of concrete, brick, and paneling and quickly disappeared into the nearby shrubbery. I had stumbled upon a congregation of camel crickets popularly known as greenhouse stone crickets, Diestrammena asynamora.

This handsome greenhouse stone cricket, Diestrammena asynamora, was photographed in my basement last fall. Our cats seem to thoroughly enjoy them and frequently leave maimed cricket bodies in conspicuous places around the house.

Greenhouse stone crickets are distinguished from other camel crickets in eastern North America by their decided preference for urban surroundings and a pair of small, closely set horns located between the bases of the antennae. Their long antennae—which may exceed three-times the body length—combined with long legs, may fool some people into thinking that they are spiders. In fact, some people call them “spider crickets.”

Their powerful jumping legs can launch them up to four feet in the air. Mature females have a long, swordlike egg-laying tube, or ovipositor that they use to deposit several hundred eggs in the soil in spring. The eggs take about two or three months to hatch. The young, wingless crickets strongly resemble the adults but are smaller in size. Once mature, the adults live for about a year. Greenhouse stone crickets overwinter as either nymphs or adults.

Greenhouse stone crickets belong to the family Rhaphidophoridae. Raphidophorids are commonly known as camel crickets because of their hump-backed appearance. They are also called cave crickets because they are often found living in and around the entrances of caves. However, they are equally at home in crevices, hollow trees, and basements, or under logs and stones. Strictly nocturnal, greenhouse stone crickets venture out during the day only when disturbed. Without wings or other sound-producing structures, these crickets never contribute to the evening chorus. However, some camel crickets are thought to drum their abdomens on the substrate in an effort to attract mates.

Some of the 200 or so species of camel and cave crickets known to occur in North America originally hail from other parts of the world. An immigrant from China, the greenhouse stone cricket first became established in the warm, moist greenhouses throughout much of Europe and North America, and is now cosmopolitan.

During heavy rains, or hot, dry days, greenhouse stone crickets will invade garages, sheds, and basements, often assembling by the dozens or hundreds. Indoors, the crickets are attracted to dark, humid spaces, such as those afforded by bathrooms and laundry rooms. Clothing and linens stored in these areas may be damaged if persistent populations of these crickets cannot find suitable plant food nearby.

Outdoors, they are commonly found on the ground, beneath stones and logs, or in piles of firewood. Areas overgrown with ivy and other ground covers provide excellent hiding places for them. Greenhouse stone crickets feed on living plants and small insects. In greenhouses, these crickets will eagerly consume seedling, flowers, seeds, or young leaves, but they seldom cause serious damage to plants. They will also scavenge other plant and animal materials.

As you read this, you can take comfort in the fact that right now, somewhere in the bowels of  your basement or elsewhere on your property, these sociable creatures are quietly taking refuge. Whether we like it or not, our steady supplies of food and water, served up in artificially warmed environments, have made it possible for these curious creatures to become a regular part of our lives.

©2010, A.V. Evans

INSECT CAMOUFLAGE-NOW YOU SEE THEM, NOW YOU DON’T!

Posted in Defense, Insects, Uncategorized with tags , , , , , , on May 26, 2009 by Dr. Art Evans

In nature, survival is the name of the game. Over the millennia, animals have evolved countless ways of avoiding danger, especially to defend themselves against predators. Insects in particular have a stunning array of defenses at their disposal. They run, jump, fly, bite, sting, and pinch. Many have bodies coated with itchy hairs or bristling with sharp, painful spines. Others have bright, conspicuously colored bodies that warn potential predators of their bites, stings, or foul tastes. Some are mimics, sporting the colors and behaviors of pugnacious, bad tasting species, but are in fact harmless themselves. But most insects protect themselves by simply remaining out of sight. And many of them do this with camouflage.

Camouflage, the French word for disguise, first appeared in popular English usage in 1917. To many, the word camouflage brings to mind the color patterns used on military combat uniforms and armaments, patterns that have since been adopted as the “official” garb of many anglers and hunters. But these and other uses of camouflage were all inspired by examples in nature, especially insects.

The simplest type of insect camouflage involves having body colors and patterns that help to conceal their bodies against specific backgrounds in their environment. For example, the leafy green hue of some praying mantids helps them to blend in among shrubs and low growing herbaceous vegetation.  In other species, such as the Carolina mantis, gray individuals are better suited for concealment on tree bark. The cryptic lifestyles of these and other predators help them to mask their presence from both predators and prey.

Toad bugs are small, squat, bug-eyed predators with grasping front legs. They hop along the shores of streams and lakes in search of small insect prey.

Toad bugs are small, squat, bug-eyed predators with grasping front legs. They hop along the shores of streams and lakes in search of small insect prey.

The shores of streams, rivers, and beaches are frequently occupied with ground dwellers whose body colors and textures are perfectly adapted for living concealed lives along the edge. One of my favorite examples is the aptly named toad bug. These small, squat, bug-eyed predators with grasping front legs hop about the wet sands and fine gravels, ever ready to pounce on even smaller insect prey.

Some grasshoppers and caterpillars have the ability to change their colors to match temporary backgrounds. Locusts can adjust their colors to match dry, open ground or lush, green vegetation. Many caterpillars avoid detection by using counter shading and are usually lighter below and darker above.

Papilio001

Not all cryptic species of insects resemble rocks, sticks, or leaves. The early stages of spicebush swallowtail caterpillars have white and black blotches on their body that makes them look like a bird dropping.

The colors and patterns of these and other insects have developed gradually through the process of natural selection. Individuals that avoid detection by predators through camouflage are able to pass along their favorable traits to their offspring generation after generation. Over time, this continual fine-tuning eventually results in colors and patterns that are ideally suited to enhancing their survival in a particular habitat. But effective camouflage isn’t just about matching colors and blending in. It is also about breaking up the outline of an insect’s body so that it looks less like a prey item to a hungry bird or lizard.

Diaphemora002

Stick insects look and behave like a stick. During the day stick insects remain almost motionless, lest they give their position away. But sometimes they will gently rock back and forth, as if they were swaying in a breeze.

Another camouflage tactic is to match the color and look of specific objects in the environment. This form of camouflage is called crypsis, a word derived from the Greek word kryptos, meaning to hide or conceal. Cryptic insects not only have the same colors as sticks, leaves (living or dead), and rocks, but their bodies are also shaped to look like them, too. Hungry predators pay little attention to these and other seemingly inedible objects when they are on the prowl for flesh.

Effective crypsis is more than just looks; it’s also about behavior. Cryptic insects have to select the right background and orientation so that color and form blend seamlessly into the right background. Landing on the wrong place, or settling in the right spot but in the wrong direction will inevitably lead to discovery and death.

geometrid larva001

With its stiff body and gray, bark-like skin, this geometrid moth caterpillar is a dead ringer for a twig.

Once, while walking down a path, I saw a twig-mimicking caterpillar stiffly protruding from the middle of the pavement.  Its gray, warty skin was a dead-ringer for a twig. Had it been on a tree or shrub, I never would have noticed it. But for whatever reasons, it had decided to conspicuously take its defensive pose out in the open on a flat, black background.

Phyllium001

The java leaf insect, cousin of the stick insect, has a flat, leaf-like body covered by a pair of leaf-like wings, all supported by six leaf-like legs.

Some of the most stunning examples of insect crypsis are species found in tropical rainforests. It is not uncommon to see these insects utilize every part of their body to help them look like something else. Java leaf insects, cousins of stick insects, have a flat, leaf-like body covered by a pair of leaf-like wings, all supported by six leaf-like legs.

dead leaf katydid001

This Costa Rican katydid is a dead leaf mimic. Note the markings on the wings suggesting the veins of a leaf.

Of course, no defense strategy is 100% effective. Birds and other sharp-eyed predators can pick up the presence of cryptic insects by their symmetrical shapes. Tropical katydids have gotten around this by having asymmetrical wing shapes and patterns. Each forewing has its own set of spots and notches suggesting leaves that have been randomly attacked by insects and fungus.

Sometimes symmetry is detected by the narrowest of shadows. Many cryptic insects purposely avoid casting shadows by pressing their bodies and appendages tightly against the substrate. Others have fringe lining their bodies and appendages that eliminates shadows altogether.

Every time I go out in search of insects, I am continually fooled by bits of vegetation that appear at first glance to be a cryptic insect. But every now and again I am rewarded for my efforts with yet another surprising example of insect camouflage. This and other revelations are constant reminders that there are lifetimes of insect discoveries to be made.

©2009, A.V. Evans

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