Sahelian tree locust (Anacridium melanorhodon)

Anacridium melanorhodon
Other common names
Sari al leil (Ar), Kokoyo (Bambara), Dobi (Djerma), Criquet arboricole (Fr), Fourdoudou (Haoussa)
Taxonomic classification
Suborder:	Caelifera
Family:	Acrididae
Subfamily:	Cyrtacanthacridinae
Tribe:	Cyrtacanthacridini
Genus:	Anacridium
Scientific name
Anacridium melanorhodon (Walker, 1870)
Geography
Native countries:
Sudan Eritrea Niger Yemen
Pest status
Known pest

Taxonomy

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

Identification

The Sahelian tree locust (Anacridium melanorhodon) is part of the subfamily Cyrtacanthacridinae which contains many of the world’s most notorious locusts. These grasshoppers are typically large-bodied, strong fliers, and capable of forming swarms under favorable environmental conditions. Their ability to switch between solitary and gregarious phases—known as phase polyphenism—underlies their capacity for sudden population outbreaks. Important locust species include the desert locust (Schistocerca gregaria), the brown locust (Locustana pardalina), the red locust (Nomadacris septemfasciata), the South American locust (Schistocerca cancellata), the Central American locust (Schistocerca piceifrons), the Bombay locust (Patanga succincta), and the migratory locust (Locusta migratoria). Many of these species are adapted to arid and grassland environments across Africa, Asia, and Australia, where periodic rainfall can trigger rapid breeding and swarm development.

Morphologically, Cyrtacanthacridinae species are distinguished by the presence of a prosternal spine and robust hind femora adapted for jumping. Wing coloration, often featuring bright hindwings with yellow, red, or rose tones, serves as a key diagnostic feature. Ecologically, migratory bird locusts play a dual role: they are important components of grassland food webs, but also pose severe threats to food security during plagues.

Identification details

Anacridium melanorhodon body color ranges from pale brown to dark grey, with almost black antennae. The tegmina have a short, dark band near the base, which is slightly pinkish-purple or yellow, with the color becoming more pronounced as the locust matures sexually. Adults show sexual dimorphism: females measure 5.4–7.3 cm and males 4.5–6.3 cm. The distal hindwing is shaded, femora of hind legs are reddish medially with three dorsal dark patches, and tibiae are purple. The eastern subspecies, A. m. arabafrum, differs by a longer hindwing fascia.

This species exhibits phase polyphenism: solitarious adults are larger and show more pronounced sexual dimorphism, while gregarious adults are smaller. Hoppers vary by phase—solitarious nymphs are green or brown, whereas gregarious nymphs are yellowish-green to greenish-yellow with black spots. A. melanorhodon may be confused with other Anacridium species, especially A. wernerellum, which has wider brown hindwing pigmentation. It can also co-occur with desert locusts, but is distinguishable by dark antennae, the basal hindwing band, and hopper speckling patterns.

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
CIRAD pest locust website	The French Agricultural Research Centre for International Development			View URL

Distribution

This species is inhabits the Sahelian zone of Africa south of Sahara with two subspecies: A. m. melanorhodon in the west (Cape Verde, North and West Africa, Sudan/Eritrea), and A. m. arabafrum in the east, extending through the Horn of Africa, Arabia, and into Iran. Their ranges overlap in Sudan and Eritrea.

For more information and distribution records see [GBIF]

Biology

The Sahelian tree locust is generally univoltine, though a second generation may occur under unusually favorable conditions. Mating follows the first rains, with eggs laid 10–20 days later. Eggs incubate for 23–65 days, and the five hopper stages take 48–69 days, producing immature adults by the dry season, when they enter diapause. Hopper instars are usually five, but may reach six to eight depending on grouping; eggs are about 6 mm long, with 140–200 per pod and 1–3 pods per female.

Although A.melanorhodon exhibits phase polyphenism, it is not highly gregarious. Swarming behavior is mostly observed in adults, even when population densities are low. Swarms migrate mainly at night, often on moonlit evenings. In Sudan, it is commonly called the “night wanderer” because of its nocturnal feeding and movement. Movements follow food availability—southward in the dry season, northward with rains, and sometimes west–east. Records of individuals far offshore show capacity for long, sustained flight. Swarms usually fly low (4–10 m) but can reach greater heights, while hoppers occasionally form marching bands, sometimes with desert locusts.

Habitat and ecology

The usual habitat of the Sahelian tree locust is open, dry woodland or thorny savanna, often dominated by fine-leaved species such as acacias (Acacia nubica, A. senegal, A. mellifera, A. tortilis, A. seyal), spiny myrtle (Maytenus senegalensis), and desert date (Balanites aegyptiaca). In wetter areas to the south, A. melanorhodon extends a short distance into the savanna zone, while in the drier north it is restricted to riverbeds and irrigated lands. Occurrences outside this range are usually due to wandering swarms or individuals following food. Natural food plants include the acacias listed above, as well as jujube (Ziziphus spp.) and caper bush (Capparis decidua). Feeding has also been recorded on herbs such as ‘Schouwia purpurea and crops like sorghum.

Young hoppers feed on grasses and sedges, while later stages and adults shift to being arborivorous, feeding mainly at night. They climb into treetops by sunrise and retreat during the heat of the day. Crop damage occurs mostly in the dry season and during adult migrations. Swarming is most common in winter but can occur year-round; swarms are usually under 1 km², though some reach 20 km, roosting in tall trees or, where absent, on lower vegetation or the ground.

Anacridium melanorhodon is highly adapted to feeding on Acacia foliage, which is low in protein but rich in defensive compounds. Normally, phenols are toxic to plant-eating insects because they attach to leaf proteins and block protein digestion after the food is eaten. A. melanorhodon can use plant phenolics like gallic acid in cuticle formation, conserving protein for growth, and shows strong tolerance to non-protein amino acids that deter other grasshoppers. These traits explain its close ecological association with Acacia and its role as a persistent pest in gum arabic–producing regions.

Natural enemies of the Sahelian tree locust include the fungus Entomophthora grylli, parasitic flies (Blaesoxipha filipjevi), wasps (Sphex spp.), spiders (Argiope spp.), mites (Eutrombidium spp.), and birds. Key bird predators—desert babblers (Argya spp.), Abdim’s stork (Ciconia abdimii), buff-backed egret (Bubulcus ibis), and grasshopper buzzard (Butastur rufipennis)—can consume large numbers and often follow swarms, along with falcons, hornbills, and Abyssinian rollers (Coracias abyssinica).

Land-use change

The Sahelian tree locust does not compete much with grass grazers but can compete with livestock (e.g. camels) for trees and shrubs, worsening overgrazing impacts on woody vegetation and soil quality. At the same time, it plays a role in nutrient cycling: during outbreaks, its fecal deposits can add substantial nitrogen to soils, comparable to significant portions of natural detrital nitrogen in arid ecosystems.

Management

Regular field monitoring is essential to assess population levels in at-risk areas, including wooded zones and tree plantations. A. melanorhodon is challenging to control even with chemical pesticides. Nymphs, usually present at low densities, are difficult to locate and rarely treated, while chemical control primarily targets swarming adults. Because A. melanorhodon typically overruns small areas, aerial spraying is often impractical. Effective treatments are carried out using manual or motorized handheld sprayers during the warm part of the day, targeting swarms roosting in trees, though wooded areas remain difficult to treat. Organophosphates (e.g., fenitrothion) are generally effective, but many adults escape by flying away during spraying.

Spores of the entomopathogenic fungus Metarhizium flavoviride were field-tested against the tree locust in White Nile State, Sudan. Applications covered 55 ha at a rate of 100 g spores/ha in 5 l of oil formulation, reducing locust populations by 66–76%.

Field trials using Metarhizium acridum on the Tree Locust have achieved 70–90% mortality within 14–20 days, with no known significant effects on non-target species.

Small amounts of Neem oil (under ~1%) are compatible with M. acridum and, when combined, enhance effectiveness against A. melanorhodon, leading to faster and higher mortality than using the fungus alone.

Pest status

The Sahelian tree locust can cause significant damage to crops and cultivated trees, particularly during the dry season. Reported damage has occurred in Mauritania, Mali, Niger, Sudan, Nigeria, Ethiopia, Cameroon, Yemen, Chad, Saudi Arabia, and Iran.

Feeding on wild trees and shrubs, such as Boscia senegalensis, can reduce forage for livestock like cattle and camels. Among grasses and cereals, damage has been noted on bulrush millet, guinea corn (especially the milky grain), maize, and rice seedlings. Other affected crops include apple, cassava, citrus, cotton, dates, guava, mango, olives, tobacco, watermelon, and trees like Balanites aegyptiaca, shea (Vitellaria paradoxa), Eucalyptus, Pithecellobium dulce, and Zizyphus species.

Gum Arabic is a key crop in Sudan’s traditional rain-fed agriculture impacted by the Sahelian tree locust. As a pest, this species can cause severe defoliation that drastically reduces yield and income for local producers, delays tapping, and creates significant socio-economic losses. Gum arabic can be contaminated by chemicals used in locust control treatments which must be suspended until gum collection is completed.

Associated organizations

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
Behind the success of desert locust control		2022		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
CIRAD pest locust website	The French Agricultural Research Centre for International Development			View URL

Specimen contributors

Collected by

• Gonzalo Mucientes Sandoval — 6 specimen(s) collected
• Luis Pascoal da Silva — 3 specimen(s) collected
• Francois Rousseu — 2 specimen(s) collected
• Sulaiman Inuwa Muhammad — 1 specimen(s) collected
• Valentin Moser — 1 specimen(s) collected

Identified by

• Gonzalo Mucientes Sandoval — 4 identification(s)
• Francesco Vitali — 2 identification(s)
• Rob Felix — 1 identification(s)