Sudan plague locust (Aiolopus simulatrix)

Aiolopus simulatrix
Other common names
Clay grasshopper, Sudan green-winged grasshopper, Criquet fouisseur (Fr)
Taxonomic classification
Suborder:	Caelifera
Family:	Acrididae
Subfamily:	Oedipodinae
Tribe:	Epacromiini
Genus:	Aiolopus
Scientific name
Aiolopus simulatrix (Walker, 1870)
Geography
Native countries:
Turkmenistan Cameroon Seychelles Turkey Maldives Syria Tajikistan Sudan Niger Nigeria Cyprus
Pest status
Known pest

The Sudan plague locust (Aiolopus simulatrix) is highly migratory and capable of forming large dense swarms. It is a particularly severe agricultural pest in Sudan, and also across the Sahel, East Africa, and parts of South Asia.

Taxonomy

For full nomenclature and taxonomic details of this taxon, see Orthoptera Species File

Identification

Locust identification in Niger

The Sudan plague locust is a species of band-winged grasshopper belonging to the subfamily Oedipodinae. It is recognized for its strong flight and characteristic hind wings, which often display vivid coloration typical of band-winged grasshoppers. These hindwings also play a role in their behavior; many species produce a loud snapping crepitation during flight, which can be heard from across a pasture or field, making them identifiable even to those unfamiliar with insect taxonomy. While most species are harmless and should not be targets of control, the group also includes some of the most destructive pest species, A. simulatrix being one of them.

Adult A. simulatrix appear mottled brown when found in dry vegetation, or brown with green coloring on the pronotum and femora when in lush habitats. This species can be identified by its antennae, which are as long as or longer than the combined length of the head and pronotum, and the absence of a ventral tubercle between the head and body. The pronotum features a single posterior transverse furrow, while the hind femur is notably broad, longer than the tibia, and marked with dark patches on both inner and outer upper surfaces, as is the tibia. The hind tibia is short, bearing nine external and ten internal spines. The forewings display clear white crossbands with diffuse markings and two uneven dark spots, while the hindwings are hyaline with dark freckling at the tips. The femora are broader than in other Aiolopus species and extend beyond the length of the tibia. Adults: female 2.1-3.7 cm long; male 1.7-3.2 cm long.

The nymphs are typically light brown with minimal markings aside from dark spots on the upper abdomen. In later developmental stages, a green stripe may appear along each side of the abdomen. When populations become dense, the species may exhibit locust-like behavior, forming loose hopper groups and showing increased dark brown spotting with the loss of green coloration. Adults may then gather into swarms.

Featured resources

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  Locust identification in Niger - French and Zarma
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Identification resources

Title	Author(s)	Year	Geographic purview	URL
FAO locust handbook identification key	FAO Desert Locust Information Service and Food and Agriculture Organization of the United Nations			View URL
Locust identification in Niger	Global Locust Initiative, United States Agency for International Development, Directorate of Plant Protection, United Nations AGRHYMET Regional Center, Le Centre National de Lutte Antiacridienne and National Network of Agriculture Chambers of Niger	2022		View URL

Distribution

A. simulatrix is found across the Sahel region of Africa, the Horn of Africa, the Middle East, and South Asia. In East Africa, the main subspecies extends southward to northern Tanzania, while A. s. femoralis ranges farther south into Tanzania, southeastern Zambia, and northern South Africa.

For more information and distribution records see [GBIF]

Biology

Aiolopus simulatrix typically produces two generations during the rainy season, with the second generation occurring farther north than the first. In regions where temperature and humidity remain high, such as irrigated areas, breeding can continue year-round. The species is highly adaptable, surviving the dry season as adults that hide in soil cracks at night and emerge to feed during warmer daytime conditions. In areas with cold winters, including Egypt, India, and Cameroon, it overwinters in the egg stage.

In Sudan and similar regions, eggs are deposited twice during the rainy season, usually in June and again between August and September. Each female lays two to three slightly curved egg pods, containing about 11–40 eggs (sometimes up to 43), enclosed in a frothy covering roughly 20–37 mm long. The incubation period varies with temperature, averaging about 18 days in early summer and extending to 23–30 days later in the season. The developing nymphs pass through five instars over a period of 35–51 days, depending on environmental conditions. Moist soil is essential for successful oviposition, and females possess an average of around 49 ovarioles.

A. simulatrix is known to form large migratory swarms. In the Sahel, this locust undertakes both daytime and nighttime long-distance flights, often alongside the Senegalese grasshopper, Oedaleus senegalensis, using winds linked to the Intertropical Convergence Zone. in Reports of A. simulatrix nymphs forming hopper bands are limited. The nymphs display density-dependent color variation—those found at low densities are typically brown, green, or a mix of both, while those in crowded conditions develop darker pigmentation on the pronotum, wing pads, and hind femora. While no direct studies have examined how population density affects A. simulatrix, Heifetz and Applebaum conducted experiments on the related species A. thalassinus. They observed that crowding did not alter body proportions or coloration but did influence behavior and physiological traits such as CO₂ output and carbohydrate and lipid levels. This suggests that A. simulatrix might show comparable responses under controlled density experiments.

Habitat and ecology

Male Aiolopus simulatrix near Aguetai, Red Sea coast, Sudan by Christiaan Kooyman

The Sudan plague locust is a grassland species most common in moist grasslands, irrigated areas, and cultivated fields, particularly near streams. It also occurs in pastures, fallows, desert grass, and thorn bush habitats, reflecting its strong Sahelian distribution.

During the dry season in Sudan it hides deep in soil cracks within croplands. In November, individuals emerge from these cracks early in the morning but, as temperatures rise, they either shelter in the shade of sorghum or climb the plants to feed. Later in the dry season, when conditions are cooler, they remain in the cracks throughout the day. With the return of moisture in March and April, the locusts emerge in large numbers during daylight, and by May, with increased rainfall, breeding begins. Populations are further augmented by migrants from surrounding regions. These movements often occur at night, with swarms strongly attracted to artificial light, though daytime flight of loose swarms has also been observed. In Sudan, such movements have led to large swarms invading and breeding in sorghum fields.

A. simulatrix is preyed on by black kites (Milvus migrans) and the bush-cricket Tettigonia cantans, which consumes 6–12 individuals daily. Adults are parasitized by flies (Blaesoxipha anceps, B. monticola, B. tertia) and by ectoparasitic mite larvae (Leptus sp.), with parasitism rates reaching up to 10%.

Land-use change

Because it is widespread in grasslands, the Sudan plague locust likely competes with livestock for forage, although this impact has not been quantified.

Management

The entomopathogenic fungus Metarhizium acridum can serve as an effective biological control when used as an oil-based suspension, though it has so far seen limited application against A. simulatrix. Chemical insecticides, typically applied as ultra-low-volume (ULV) sprays, remain the primary means of control and should be used only in cases of severe infestation. In non-cereal crops, treatments aimed at other pests or general grasshopper control usually manage A. simulatrix populations sufficiently.

In Sudan, control of A. simulatrix has included night-time discing of the soil, which traps grasshoppers sheltering in cracks and reduces their emergence during the day. Adjusting sowing times for sorghum and other cereal crops can also be effective, with the choice between early or late planting depending on local conditions. Early-sown crops are often robust enough to withstand damage, while late-sown crops may avoid the period of peak grasshopper abundance before reaching the milky-grain stage. Successful application of these methods requires careful consideration of local environmental and infestation patterns.

Pest status

Among the Aiolopus genus, four species—A. simulatrix, A. strepens, A. longicornis, and A. thalassinus—are considered economically significant pests. Of these, the Sudan plague locust, A. simulatrix, is the most destructive, causing severe damage to grain and various other crops. In Sudan it is regarded as the most important species as a pest of grain crops in the east-central rainlands. Reported outbreaks and damage have been recorded from Cyprus, Libya, Egypt, Yemen, Iran, Tajikistan, Pakistan, India, Bangladesh, Sudan, Ethiopia, Senegal, Mali, Cameroon, and northeastern Nigeria.

A. simulatrix is a serious pest of sorghum, with serious losses documented in Cameroon, India, and Sudan. The locust is particularly destructive to seedlings and to grain at the milky stage, when swarms may cause complete crop loss—as occurred in Sudan in 1946. The extent of damage varies with invasion timing, weather conditions, and crop stage, but most severe destruction occurs when sorghum is very young or in the milky stage.

Beyond sorghum, the species also attacks a wide range of crops, including citrus, clover, geranium, lucerne, maize, millet, rice, sugarcane, wheat, forage and pasture plants, bulrush millet, and cotton. Additional hosts reported for A. simulatrix include chickpea, groundnut, oat, pea, and several grasses.

Organizations associated with the Sudan plague locust

Organization name	Acronym	Website	Type	Focus	Focus keywords	Geographic purview
Ministry of Agriculture Sudan		View	Government		Agricultural development	Sudan

Resources

Title	Author(s)	Year	Geographic purview	URL
Supplementary environmental assessment (SEA) for USAID funding of locust or grasshopper pesticide usage in Sudan	United States Agency for International Development	1990		View URL
FAO locust handbook identification key	FAO Desert Locust Information Service and Food and Agriculture Organization of the United Nations			View URL
CABI Green Muscle education videos	Centre for Agriculture and Bioscience International	2021
Locust identification in Niger	Global Locust Initiative, United States Agency for International Development, Directorate of Plant Protection, United Nations AGRHYMET Regional Center, Le Centre National de Lutte Antiacridienne and National Network of Agriculture Chambers of Niger	2022		View URL

Specimen contributors for this species

Bionomia links specimen records in GBIF to the people who collected and identified them. Each list shows the top 20 for this species. Read more…

Identified by

People who determined the taxonomic identity of specimens of this species.

• Rob Felix — 1 specimen identified