Bug Day (13): “Warrior” Grasshopper
A century ago, this grasshopper was known as the Warrior. In a richly detailed 1915 memo, E.D. Ball Ph.D., Director of the Utah Agricultural Experiment Station, describes decades of battles against massive swarms of Camnula pellucida. Workers using horse-drawn canvas dragnets called “balloons” collected them by the ton for a bounty of a penny a pound. A rather small swarm in one Utah county in 1913 yielded 28 tons of the insects, while a larger swarm in 1902 yielded 274 tons. These catches amounted to at most two to five percent of the swarms. Approximately eight million juvenile or adult hoppers made up a ton, while the total swarm, based on a count of the number of bugs in a square yard, was around 3.5 billion for the small swarm of 1913, and 200 billion in the large invasion of 1902. Ball’s estimate of the number of eggs in the breeding grounds yielded a count of about one billion eggs per acre. Modern counts find anywhere from 3,000 to 100,000 eggs per square foot.
Today, long-distance swarms of biblical magnitudes are unknown. Most swarms observed in recent times involve smaller numbers and distances of a few hundred yards at a time. But the Clear-winged Grasshopper can still do significant damage. In Oregon in 2010, swarms of them darkened the sky, slicked up highways, sent people running for cover, and chewed major gaps in commercial crop yields.
Helmuth Rogg of the Oregon Department of Agriculture is quoted as saying, “They are the lawnmower of the prairie…. The biggest biomass consumers on the North American prairie are grasshoppers — not cattle, not bison, not antelope.” The pests can reduce rangeland forage by 80 percent in areas as large as 2,000 square miles. Agricultural biologists at the county, state, and province levels in the U.S. and Canada annually monitor the grasshopper and issue guarded forecasts.
This bug is today named for its rear wings, which are generally clear and transparent except for the veins. The wings only emerge, dry out, and become functional several weeks after the eggs hatch. The hungry wingless nymphs do much of the crop damage. They can crawl or make short hops, and they advance like a massive chewing army devouring just about anything in their path. When they can fly, they seek out their favorite food group, the grasses. In particular, they love an introduced hybridized and fertilized grass that people have planted in astronomical numbers: wheat. This grasshopper’s eggs hatch early in the year, just in time for the nymphs to feed on young green spring wheat. Wheat has been a boon to this bug. Experiments showed that C. pellucida raised on wheat grew faster, bigger, stronger, and laid up to 20 times more eggs than those with access only to the native grasses of the region. If unchecked, a cohort of nymphs will completely destroy a wheat crop. Barley, including foxtail barley, is also among the bug’s favorite foods. Swarms may also invade vegetable crops and eat onions, lettuce, cabbage, and peas. Even blueberries are not safe.
The females do most of the eating. They are from twice to three times heavier than the males and have bigger jaws. Once they can fly, the males are mainly concerned with reproduction. They flutter in huge numbers at the breeding grounds waiting for the females. If a female is receptive, they couple together for about an hour. Then the female deposits her eggs. She digs a hole in the soil about an inch deep, lines it with a tough cement-like coating, pushes about two dozen eggs into it, seals the top, and then covers it with dirt. She then flies back to the feeding area and bulks up. She returns to the breeding ground, mates again, and lays more eggs. She may do this eight times in favorable conditions, laying about 180 eggs. The males, having mated, eventually die on the breeding grounds. Life expectancy for the females is about two months. The eggs stay in their pods over the winter. Autumn wildfires burn quickly over their heads and they suffer no injury. An exceptionally hard and deep frost will kill most of them, but the average winter does them no harm. In the spring they hatch and emerge, usually all of them within a day or two.
The number of grasshoppers that hatch each season varies greatly. Generally, warm dry weather favors them, and prolonged drought boosts the chances of big swarms. But other factors weigh also, notably the prevalence of bugs that prey on the grasshopper’s eggs. Bee flies, field crickets, and Epicauta species of blister beetles, all feed on grasshopper eggs and can significantly reduce their number. A fungus, Entomophora macleaodii sickens and kills them; common field ants, Formica fusca, carry the fungus and will transmit it to the grasshoppers on contact.
Birds, of course, will eat the grasshoppers, but Dr. Ball’s narrative makes no mention of them. The famous story of the California seagulls who descended from the sky and saved Mormon crops by gobbling up “Rocky Mountain crickets” in 1848 refers to a different species of grasshopper, Melanoplus spretus, now extinct. For the indigenous people who thrived in the area before the Europeans, grasshoppers were manna from heaven. Paiute, Goshute and Shoshone collected them avidly, ate them roasted, or ground them into mush and meal for cakes. They are rich in protein, carbohydrates, and other nutritional values.
The burden of Dr. Ball’s 1915 memo was that controlling the Warrior grasshopper once it became an adult was a losing proposition. You had to locate the breeding grounds and destroy the eggs before they hatched. He recommended hoeing, tilling, and plowing under. Today applications of the pesticide Dimilin (diflubenziron) prevents eggs upon hatching from developing a chitin exoskeleton, so that they die of exposure. In the alternative, a wide array of other pesticides will kill the adults, albeit with a high risk of collateral damage to humans and other creatures.
Here in the park, this Clear-winged Grasshopper has plenty of grasses to chew on, including foxtail barley. Pesticides are not allowed here. This individual didn’t seem to have any company in the immediate vicinity. So we can’t anticipate that this “lawnmower of the prairie” will replace the stinky, noisy mechanical contraptions that now denude the park’s grassland.
More about them: Dr. Ball UtahHumanities IDTools.org Wyoming Kistner-Thomas Oregon Oregon AgCenter Manitoba Pickford BugGuide
Tomorrow: Potato Mirid
Oh, sorry, you already posted a (different) link to the same paper.
Oops. Sorry. You already provided a link to that paper.
Great photo, and nice story.
Here are some photos of each instar (note how different each is), as well as of the clear (“pellucid”) hind wing:
http://wci.colostate.edu/Assets/pdf/Grasshopper/ClearwingedGH.pdf