Grasshoppers: Biology and ecology

Grasshopper nymphs on leaf: First instars (i.e., 1st stage nymphs) of differential grasshoppers, Melanoplus differentialis, feeding on soybean. They will go through several molts before maturing to an adult.Grasshopper nymphs on leaf: First instars (i.e., 1st stage nymphs) of differential grasshoppers, Melanoplus differentialis, feeding on soybean. They will go through several molts before maturing to an adult. (in the background, out of focus, is a 1st or 2nd instar of the redlegged grasshopper, M. femurrubrum) (USDA-APHIS 1989). (Photo Marlin E. Rice)

The adult female grasshopper deposits a cluster of eggs during late summer or early fall by inserting her abdomen into moist soil. Along with the eggs the female deposits a frothy secretion that will harden around the eggs and provide protection. The eggs will then overwinter in the soil. The eggs will incubate in the soil and the small, wingless nymphs will emerge the following spring. The time required for hatching is variable and depends on the grasshopper species and soil temperatures (USDA-APHIS 1989).

Following eclosion, the grasshopper nymphs will molt through several stages (with the number of stages depending on the species). Each grasshopper species has specific requirements for development (USDA-APHIS 1989). However, nymphs and adults require warm (> 68oF) and sunny weather to be active (Capinera et al. 2004).

Grasshopper diseases: Adult differential grasshoppers, Melanoplus differentialis, that have been infected with either "summit disease," Entomophaga grylli, [left] or an unidentified bacterial pathogen [right]. (Photos Marlin E. Rice)Grasshopper diseases: Adult differential grasshoppers, Melanoplus differentialis, that have been infected with either "summit disease," Entomophaga grylli, [left] or an unidentified bacterial pathogen [right]. (Photos Marlin E. Rice)

Warm and dry weather favors grasshoppers so that their populations may be larger than during other environmental conditions (Streett 1987). While warm weather enhances grasshopper development and survival, warm weather combined with extended periods of high relative humidity will favor entomopathogens that attack grasshoppers. This is particularly true for the fungal pathogen, Entomophaga grylli, or "summit disease." Grasshoppers affected by this entomopathogen will climb to the top, or summit, of a plant and grasp the plant tightly in a “death grip” before dying in a stiffen position with one or both hind legs extended backward. This fungus is primarily responsible for reducing grasshopper abundance under warm and humid environmental conditions (Streett 1987). Grasshoppers affected by bacterial pathogens often hang loosely from plants and break apart through a rotting process caused by the disease.