Posts Tagged ‘grasshopper’

Generals on the March

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Tuesday, November 20th, 2012
Horse Lubber Grasshopper

Horse Lubber Grasshopper © Sheri Williamson

Generals on the March by Tom Wood and Sheri Williamson

A generous late summer “monsoon” season in the desert grasslands of the Southwest translates to a fall population boom for many wildlife species. Some of the “boomers” are easier to see than others, including the gigantic grasshoppers known as Horse Lubbers. They’re one of the two largest grasshoppers in North America (the other being the Eastern Lubber). A mature female may be 2.75 inches in length and weigh as much as three male Black-chinned Hummingbirds!

Many of our human neighbors here in southeastern Arizona know the Horse Lubber as the “Mexican General,” a colloquial name inspired by its bold pattern of bright yellow accents on a background of black and dark green, like a high-ranking officer in full dress uniform. Grasshoppers often have colorful hindwings, and a few are quite colorful on close inspection (the Rainbow Grasshopper, for example), but no other grasshopper in the Southwest is as in-your-face conspicuous as the Horse Lubber.

Like many desert insects, Horse Lubbers depend on the short-term abundance of food resulting from the late summer rains. When “monsoon” thunderstorms transform the desert into a virtual all-you-can-eat salad bar, lubber nymphs hatch from eggs laid the previous year and begin to gorge themselves. As they reduce the food supply in one area, they march on to greener pastures, passing through several instars (growth stages) as they go. Early instars are chunky and wingless. By the final stage, they have slimmed down and grown wings for greater mobility.

The lubber boom might seem to be a boon for predators, but it pays to be suspicious about a critter that’s abundant, conspicuous, and easy to catch. You’ve probably already figured out that the gaudy attire and sluggish behavior of Horse Lubbers are aposematic, a warning to potential predators of well-armed prey. Like Monarchs and Pipevine Swallowtails, the big ‘hoppers are infused with toxic chemicals that make them unpalatable, but making a predator nauseous is a Pyrrhic victory. The preferred outcome is not to get eaten in the first place. Threatened lubbers start by hissing and flashing their bright salmon-red hindwings. If that doesn’t work, they’ll spray their attackers with noxious chemicals, like six-legged skunks. It doesn’t take too many such encounters for predators to learn not to mess with lubbers. Our pet chickens enthusiastically chase after any small, cryptically colored grasshoppers that find their way into our yard, but they give the big black ones a wide berth.

We think of grasshoppers as herbivores, but Horse Lubbers like a little meat in their diet. They’re not fussy; carrion is fine fare, and they’re not above cannibalism. As with skunks, the sluggish and fearless behavior of lubbers makes them vulnerable to traffic. Those that don’t make it across the highway may become “road food” for their traveling companions. In fact, their chemical defenses are so successful that about the only animal that can stand to eat a Horse Lubber is another Horse Lubber. As our collegue Pete Corradino discovered, Loggerhead Shrikes in Florida will eat Eastern Lubbers after letting them “mellow” a bit to break down the toxins, but we haven’t observed this behavior in Arizona. Maybe Horse Lubbers are “spicier” than their southeastern cousins?

Grasshopper the Jumping Gluttons

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Friday, July 6th, 2012

Two-striped Grasshoppers by Kent McFarland

Grasshoppers are known for jumping and eating. Their strong hind legs and specialized elastic fibers in their knees allow them to jump twenty times their body length. Pound for pound, a grasshopper can eat up to 20 times as much vegetation as a steer, according to the Oklahoma Cooperative Extension Service.

Unlike many herbivorous insects, most grasshoppers will eat many different species of plant. Some can wipe out crops. Others, like the Two-striped Grasshopper (Melanoplus bivittatus), eat plants that are toxic to grazing cattle. When the going gets tough, grasshoppers may even eat dry plants on the ground or even scavenge weak or dead grasshoppers.

Video of a Two-striped Grasshopper eating by Kent McFarland

The Creosote Bush Grasshopper (Bootettix argentatus), found in the southwest, is the only grasshopper among the more than 660 species known in North America that feeds on only one plant, its namesake the Creosote Bush. The leaves have a resinous coating that makes them indigestible to most herbivores. There’s more resin in the buds and young leaves compared to the mature leaves. To combat the resin the grasshopper adds more oxygen in the digestive process that helps to make the resin more digestible. The resin content throughout the plant lowers during the evening hours for some reason. Of course the grasshoppers feed mostly during these hours.

Grasshoppers have powerful mandibles to rip plants into tiny pieces. Salivary glands in the mouth begin to digest the food chemically. The food passes from the mouth through the muscular pharynx down the esophagus to and to the crop. Like a bird’s crop, this organ can hold food until later. From the crop it enters the gizzard where the food is ground. Sliding down to the stomach, it is attacked by enzymes that break the food down even further. Nutrients are absorbed and the waste products are converted into dry pellets called frass and dropped to the ground.

Rocky Mountain Locust (Melanoplus spretus) ranged through the western half of the the U.S and Canada. Early European settlers described massive swarms. One famous sighting of a swarm was estimated to cover 198,000 square miles, weighed 27.5 million tons, and had about 12.5 trillion grasshoppers in it. Thirty years later they were extinct. The last one was found in Canada in 1902. It is thought that plowing and irrigation somehow disrupted the natural cycle of this grasshopper dooming it to extinction. Imagine the amount of vegetation that these swarms must have eaten.

Recently, for the first time that I can ever recall, I lay down and very closely watched the grasshoppers feeding in my garden. I was reminded of the old television series “Kung Fu” when the master questioned the student.

Master Po: Close your eyes. What do you hear?
Young Caine: I hear the water, I hear the birds.
Po: Do you hear your own heartbeat?
Caine: No.
Po: Do you hear the grasshopper which is at your feet?
Caine: Old man, how is it that you hear these things?
Po: Young man, how is it that you do not?