What are the similarities and differences between a Grasshopper and a Locust?

The Grasshopper and the Locust are both insects in the Acrididae family of grasshoppers, groundhoppers, and locusts. They are acridids. 

The Grasshopper has no sub-family, whereas the Locust has three sub-families – 1) Spur-Throated Grasshopper, 2) Band-Winged Grasshopper, and 3) Slant-Faced Grasshopper.

The Grasshopper does not always become a Locust, whereas the Locust is a Grasshopper. 

The difference is the way the Grasshopper and the Locust react in high density populations (when they are under crowded conditions). When they are crowded, their behaviour, morphology, appearance, physiology, habits, and ecology change over several generations, which is called a phase change. The phase change occurs from a solitary phase to a gregarious phase.

The Grasshopper stays in the solitary (or individual) phase, whereas the Locust is in the gregarious (or swarm) phase. In the swarm phase, the Locust forms highly mobile, dense groups and flying swarms of adults (winged locusts).

The phase change from Grasshopper to Locust occurs when ecological condtions occur (external, physical surroundings), such as sufficient vegetation for food, good conditions for breeding, good moist soil for laying eggs, and low mortality (death) rates. 

In the phase change, the Locust undergoes a biological change, which means that the eggs hatch at the same time and they form dense egg-beds, from which the newly-hatched hoppers band together. After growing their wings, the immature adult Locusts form swarms to look for food.

In the phase change, there is a morphological change to help the adult Locusts fly over long distances to look for food (crops and vegetation). They often change shape, colour, or colour pattern. The Grasshpper in the solitary phase is usually green, whereas the Locust in the gregarious phase looks brown or black with orange spots. The male and female Grasshopper in the solitary phase look similar, but the female is larger, whereas the male and female Locust in the gregarious phase look the same and are the same size.  

In the phase change, there is generally a physiological change to help the population increase. The female Grasshopper in the solitary phase lays a lot of eggs, whereas the female Locust in the gregarious phase lays fewer eggs which are larger and more resistant to mortality. 

The Grasshopper in the solitary phase remains in a limited location called a recession area (it is not migratory), whereas the Locust in the gregarious phase changes its habits and habitats to live and breed in a wide range of regions and countries called an invasion area (it is migratory).

Information sources: Department of Agriculture, Fisheries, and Forestry, Australian Government; and the United Nations Food and Agriculture Organization (FAO) 

Photographer: Martina Nicolls 

Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM