Carolina Grasshopper

Phenology

Spring
Carolina grasshopper eggs hatch in late May and June and grow through 5 or 6 molts (instars). Because they develop into adults through Incomplete metamorphosis, the young look much like the adults (there is no caterpillar stage) and are called nymphs.

Summer
New adults begin appearing in late June after their final molt, complete with functional wings. In late summer, females lay clusters of about 50 eggs, enclosed in a curved egg case (ootheca), 4cm (1.6in) deep in the soil.

Fall
All adult Carolina grasshoppers die after the first hard freeze in late fall.

Winter
The eggs of the Carolina grasshopper overwinter in their egg case in the soil. The embryos inside the eggs stop developing during winter (diapause) and will complete their development in spring.

Behavior

All locusts are grasshoppers, but not all grasshoppers are locusts
The Carolina grasshopper is a rarely-destructive member of the locust family (Acrididae). Several species of locust form immense swarms capable of devouring crops and creating foods shortages. The Carolina grasshopper, also called the Carolina locust, seldom swarms.

Two Phases of Locust
Locusts are solitary for most of their lives, preferring to graze harmlessly and interact with other members of their species as little as possible. If conditions are just right, they enter a “gregarious” phase, forming devastating swarms.

Serotonin, Dr. Jekyll, and Mr. Hyde
Swarming is a response to overcrowding after a good hatch year. When the food supply dwindles, the ordinarily solitary grasshoppers become clustered together. The increased contact between grasshoppers causes them to produce more serotonin.

In humans, serotonin is the “happy chemical” which regulates anxiety and mood. In grasshoppers, serotonin causes the normally antisocial insect to be more tolerant of large groups (gregarious) and triggers an increase in feeding and breeding, which accelerates population growth. In their gregarious phase, they become darker in color, develop stronger muscles, and are much more mobile. The locusts look so different from their solitary stage that until the 1920s, entomologists thought they were two unique species.

Avoiding Cannibalism by Moving as a Group
Cannibalism is common in locusts but less so in their solitary phase when their only contact with each other is during mating. In their gregarious phase, they avoid being eaten by moving forward when other locusts approach, creating a massive directional flow of individuals. Grasshoppers that don’t “go with the flow” are at greater risk of being attacked. As the locusts reach adulthood and can fly, the group’s movement continues in the air. This behavior creates destructive swarms that can ravage a region’s food supply. A better understanding of swarming behavior is an essential step towards desperately-needed control of this destructive insect.

Physiology

Winter Egg Survival
How the eggs of the Carolina grasshopper can survive the cold and dry conditions of winter, buried a few centimeters below the soil surface, is not entirely understood. As the female deposits her egg case (ootheca), she secretes a sticky substance that encloses the capsule in a layer of cemented soil. This layer may keep the insect eggs from losing water as they wait for spring in a state of diapause.

Diet

Carolina grasshoppers are herbivores (and at times cannibalistic), feeding on any available plants. They are considered a minor pest to crops and feed on wheat, potatoes, and corn.

Lifespan and Mortality

Adult Carolina grasshoppers die after the first hard freeze in fall.

Predators
Carolina grasshoppers are preyed on by almost any animal with the ability to catch them, including many birds, mammals, spiders, snakes, toads, and frogs.

Climate Vulnerability

A study in the Konza Prairie in Kansas suggests that a decline in the grasshopper population is linked to higher carbon dioxide levels in the atmosphere. Although the increase in carbon dioxide helps prairie grasses grow larger, the nutrient levels in the plants don’t change. The grasshoppers are taking in less nutrition with each bite.

Never stop learning

Culinary History: Chapulines are roasted grasshoppers and have been a Mexican delicacy for thousands of years.

Entomophagy: the practice of eating insects.

References

Articles

Grasshoppers of the Choctaw Nation in Southeast Oklahoma https://extension.okstate.edu/fact-sheets/grasshoppers-of-the-choctaw-nation-in-southeast-oklahoma.html

Chapulines: Cooked Grasshoppers https://www.thespruceeats.com/chapulines-mexican-grasshoppers-2342567

Edible insects: Future prospects for food and feed security https://www.fao.org/3/i3253e/i3253e00.htm

Locust swarms’ high’ on serotonin http://news.bbc.co.uk/2/hi/science/nature/7858996.stm

Surviving amongst cannibals https://www.mpg.de/6358514/locusts_cannibalism_polyphenism

When Grasshoppers Go Biblical: Serotonin Causes Locusts to Swarm https://www.scientificamerican.com/article/when-grasshoppers-go-bibl/

Videos

Five Facts about the Carolina Grasshopper https://www.youtube.com/watch?v=YCuc73z4yQE

Freaky Food: New York’s Grasshopper Tacos https://youtu.be/fPr87z7GfQc

Research Papers

Welti, Ellen & Roeder, Karl & de Beurs, Kirsten & Joern, Anthony & Kaspari, Michael. (2020). Nutrient dilution and climate cycles underlie declines in a dominant insect herbivore. Proceedings of the National Academy of Sciences. 117. 201920012. 10.1073/pnas.1920012117. https://doi.org/10.1073/pnas.1920012117

Branson, D.H. and Vermeire, L.T. (2007), Grasshopper egg mortality mediated by oviposition tactics and fire intensity. Ecological Entomology, 32: 128-134. https://doi.org/10.1111/j.1365-2311.2006.00847.x

Anstey ML, Rogers SM, Ott SR, Burrows M, Simpson SJ. Serotonin mediates behavioral gregarization underlying swarm formation in desert locusts. Science. 2009 Jan 30;323(5914):627-30. doi: 10.1126/science.1165939. PMID: 19179529. https://doi.org/10.1126/science.1165939

Vishwesha Guttal, Pawel Romanczuk, Stephen J. Simpson, Gregory A. Sword, Iain D. Couzin Cannibalism can drive the evolution of behavioural phase polyphenism in locusts Ecology Letters, 8 August 2012; DOI: 10.1111/j.1461-0248.2012.01840.x http://dx.doi.org/10.1111/j.1461-0248.2012.01840.x