This week Bug of the Week received several inquiries about strange happenings along beaches from Virginia to Delaware. Thousands or perhaps millions of grasshoppers appeared in the surf and on the sand much to the chagrin of swimmers and sunbathers. Was this a rerun of the eighth biblical plague or, as one witness put it, “Is this some kind of a really bad omen?” From images sent to me, it appears that this remarkable event was the result of an exceptionally large brood of differential grasshoppers taking a wrong turn and winding up in the drink. Differential grasshoppers are part of a clan known as spur-throated grasshoppers. These plant-munchers include some of our most infamous and destructive grasshoppers. In the years 1874 to 1877, vast swarms of migratory, spur-throated grasshoppers devastated crops from the Rockies to Texas. A single swarm observed during this period was estimated to contain 124 billion insects. Yikes!
When hassled by predators on entomologists, grasshoppers regurgitate "tobacco juice", a noxious mixture of defensive chemicals derived from plants.
In a typical year, differential grasshoppers feed on herbaceous plants like ragweed and sunflowers and grasses growing in meadows, roadside swales, and the boarders of woodlots and agricultural fields. When conditions are favorable and populations build, they become pests of grains like wheat and barley, corn, alfalfa, and soybean. Differential grasshoppers begin life in the spring as small nymphs that hatch from eggs deposited in the soil by their mothers during the previous year. The nymphs eat herbaceous plants in spring and early summer. These wingless nymphs often move through a field in a phalanx-like band, munching plants along an advancing front.
Differential grasshoppers were chilling on the beach last week.
After feeding for several weeks, they molt into winged adult grasshoppers. When they have depleted vegetation in one area, these strong fliers take wing, sometimes in unison, and fly toward greener pastures. On particularly warm days, when temperatures exceed 86° F, differential grasshoppers will take flight in an apparent attempt to escape the heat. Swarms of grasshoppers have been observed by pilots of airplanes at altitudes on 1,400 feet and one “marked” differential grasshopper was observed to move 20 miles in two days. With the wonderful wet growing conditions we enjoyed this year, a lush crop of weeds and vegetation has grown throughout the region. It appears that a bumper crop of differential grasshoppers was also produced. Whether it was an attempt to escape the heat or a search for more food, thousands of grasshoppers took flight last week and a fickle wind deposited them on the seashore. While vacationers were dismayed, bug geeks were delighted at this rare event that is unlikely to be witnessed again in the near future.
References:
We thank Frank, Shawn, and Lori for the inspiration for this episode. An Introduction to the Study of Insects by Borer, DeLong, and Triplehorn and the website noted below were used as references for this Bug of the Week.