LOYAL. LOCAL. COMPLETE.
By late summer, we all have long-legged grasshoppers in our yards fiddling the night away, eating, and making merry. In Tooele County, just west of Salt Lake City on I-80, the news is full of stories about the grasshopper invasion, which seems to occur there every seven years. It actually follows drought cycles. Currently, the state is under moderate drought, but last year Utah was under extreme drought. That was the incubator for the current population.
Grasshoppers respond to drought and their population explodes. They run out of plants to eat, so they travel in swarms searching for more food. They consume, leave the land barren, and move on. The connection with drought is because they lay eggs just under the soil surface, which is normally damp. The natural fungus and viruses destroy most of the eggs. When the soil in an area normally lush with grass becomes parched, worms, grubs, and nematodes go deeper. Fungus goes dormant and this allows a large percentage of the eggs to survive. Nymphs emerge from the soil and compete with each other. They consume every plant and as the greenery disappears those tan-green insects move in, mass consuming everything in their path.
Grasshoppers grow quickly. They need massive quantities of food. Each one needs to eat 50 to 250% of its body weight per day. A cow only eats between 1 and 2% of their body weight. A locust is a grasshopper. There are over 6000 species of grasshoppers and about a hundred are classified as locusts. The locust has a little more tendency to mass together and swarm, but all grasshoppers do it. When there is plenty of food and smaller populations, they act alone. When food is scarce and populations explode, their instinct is to herd up and move as a giant swarm.
Grasshoppers have about two generations per summer. The eggs take two weeks to hatch and the young take six weeks to develop into adults. Adults will begin laying eggs in three weeks and live about eight weeks total. They lay massive numbers of eggs, expecting most to be destroyed. During a drought, too many survive.
In 1931, swarms of grasshoppers descended over Iowa, Nebraska and South Dakota, destroying thousands of acres of crops. Those who experienced it said it wasn’t an exaggeration to say that you could scoop them by the shovel full. The grasshoppers ate the corn to the ground, leaving not a stalk standing. This continued every summer until the late 30s when it finally began to rain. By 1937, it was so bad that states deployed the National Guard. They used disks, earth-moving equipment and even flamethrowers to try to stop them.
Grasshoppers first appeared in the African Savanna 300 million years ago. They’ve changed little over time. They are classified in the order Orthoptera, which includes grasshoppers/locusts, crickets and katydids.
Young grasshoppers crawl or jump using their hind legs, which are so strong that they can jump 20 times their own length. That would be comparable to a person jumping half a football field from a standing start. All grasshoppers can fly. We may see many without wings, but they’re just not mature. Only true adults have wings.
Grasshoppers hatch from an egg and the tiny yellow-green nymph climbs out of the soil to begin eating. They look similar to adults, just tiny. As they eat and grow, the nymph sheds its skin about five times, emerging bigger and with slightly morphed body parts. They never go through a caterpillar-type radical metamorphosis. Instead, they molt and emerge multiple times with a slightly more adult-like body. Later stages begin to have wing buds, but only the last transition emerges as a fully developed adult with wings. Adults travel by flying but have to use their strong legs to launch them up and forward for takeoff.
Grasshoppers typically fly low and a few feet a a time. When in active swarm mode they can fly 20 miles per hour at heights of 1,000 to 3,000 feet above the ground covering 70 miles per day. A giant swarm will completely saturate a radar image.
They have a typical insect body with a head, thorax and abdomen. Their smell receptors are along the antenna. They have five eyes; two big compound eyes and three smaller eyes across the forehead letting them pick up light and shapes in every direction. Their ears are placed along their abdomen. They really do fiddle for a mate. They rub a series of small spines on their hind leg across a scraper on the wing. It’s like running a thumbnail across the teeth of a comb. Males fiddle to establish their territory and to attract females. Like a cicada, the female has an ovipositor near her tail which she uses to inject a mass of 70 eggs a half inch into the soil. She will repeat this to leave three different egg masses.
The grasshopper’s crude stomach uses enzymes to break down plant material. Their insides are filled with fluid that gets pushed to their brain and then oozes back down providing nutrients to all the cells. As a defense mechanism, their first tactic is to run away, but if cornered they will regurgitate or spit up a vile brown liquid. The toxic liquid consists of gastric enzymes and partially digested food. Every child has had that “tobacco spit” in their hands from a captured hopper. The juices are unpleasant tasting to birds and poisonous to small insect predators.
The grasshopper is a source of food for much of the world. They are a good protein source when cleaned and cooked. The Quran and the Bible both have stories of locust invasions used as punishment. They contain tales of surviving on locusts and wild honey. Aesop’s tale compared the carfree grasshopper and the industrious ant. In truth, they both spend their time searching for food. An ant needs stores to get his colony through the winter. The grasshopper depends on eggs and dormant nymphs sheltered underground. They don’t need food stores. They live a solitary life unless food runs short, then they will mass together to invade new lands.
(Terry Sullivan’s fascination with science started as a child watching Carl Sagan’s “Cosmos” and James Burke’s “Connections” on PBS. He is the retired technology and curriculum director for the Shiloh School District. Email him at armchair@sullivantech.net)