The red locust, Nomadacris septemfasciata, is a large grasshopper native to sub-Saharan Africa, known for its ability to transform into a devastating swarming pest. The species name “septemfasciata” refers to the seven transverse bands visible on its wing covers.
Physical Characteristics and Life Cycle
Adult red locusts are substantial, with males measuring 60-70 mm long and females 60-85 mm. Their coloration is light beige and brown, though their hind wings are notably reddish. A consistent feature is a vertical blackish band bordered with white or yellow, located beneath the eyes.
The life cycle of the red locust involves one generation per year. Females deposit egg pods, each containing between 20 and 195 eggs, into moist soil. These eggs incubate for about one month before hatching into wingless hoppers. Hoppers then undergo six to eight molting stages over about two months before developing into winged adults.
The Solitary and Gregarious Phases
The red locust exhibits phase polyphenism, existing in two distinct forms: solitary and gregarious. In its solitary phase, locusts are greenish or brown, prefer isolation, and are non-migratory. Their numbers are low, posing no major economic threat to agriculture.
A transformation occurs when increased population density triggers a switch to the gregarious phase. This is often stimulated by drought followed by abundant rainfall and rapid vegetation growth, concentrating populations in smaller suitable areas. As hoppers become more crowded, physical contact initiates behavioral and anatomical changes.
Gregarious hoppers develop distinct bright yellow, brown, or black colorations and form cohesive marching bands that can move hundreds of meters daily. Gregarious adults form dense swarms that fly with the wind during daylight hours, covering vast areas, though rarely moving more than 20-30 kilometers in a day. This phase change enables the formation of large, destructive swarms.
Geographic Range and Outbreak Areas
The red locust is found across southern and eastern Africa, south of the Sahara. While isolated specimens can appear in cultivated areas, populations usually remain at low densities in subtropical grasslands. The species seeks out moist environments, such as seasonal floodplains, which serve as prime habitats.
Outbreak areas are a defining aspect of the red locust’s geography. These are specific, seasonally flooded grassland regions where solitary populations persist and from which large-scale plagues can originate. Significant outbreak areas include the Rukwa Valley in Tanzania and the Mweru wa Ntipa marshlands spanning the border of Zambia and the Democratic Republic of Congo. Other sites are in Malawi and Madagascar, with observations in Sahel regions like Cape Verde and around Lake Chad.
Economic Impact and Management
The red locust poses a significant economic threat due to its voracious feeding habits. Swarms can consume vast quantities of crops, including maize, sorghum, and sugarcane, along with wild herbaceous species and trees. This damage directly jeopardizes food security and the livelihoods of millions, particularly subsistence farmers. A single square kilometer swarm can consume as much food in one day as 35,000 people.
Managing red locust populations relies on a preventive strategy focused on monitoring and early warning systems. This involves regular surveys to detect population density increases within known outbreak areas before hoppers develop into destructive swarms. Early detection allows for targeted interventions to prevent widespread infestations.
Control strategies include chemical agents, though biological control methods are increasingly utilized. Biopesticides, such as those based on the entomopathogenic fungus Metarhizium acridum, show promise in controlling nymphs and adults. These biological agents offer a more environmentally sustainable solution by specifically targeting locusts and minimizing harm to other wildlife.