Desert Locust

• The switch from the solitary to the gregarious phase is triggered by repeated physical contact on the hind legs, which sets off a surge of serotonin in the nervous system and completely changes the animal's behaviour within hours.
• A swarm can cover hundreds of square kilometres, travel more than a hundred kilometres a day and eat as much food in one day as tens of thousands of people.
• Its plagues are described in texts more than three thousand years old and still cause food emergencies in the Horn of Africa.
• It changes personality. Under normal conditions it is solitary, green and elusive; when rain concentrates the vegetation and individuals brush against one another, it transforms into the gregarious phase: it changes colour to yellow and black, becomes more active, eats more and seeks company instead of avoiding it.
• The trigger has been pinpointed precisely: repeated rubbing of the hind legs sets off a serotonin cascade that brings on the transformation in a matter of hours.
• A swarm can cover hundreds of square kilometres and contain tens of billions of individuals; a swarm of one square kilometre eats as much in a day as 35,000 people.
• The 2019-2021 plague in the Horn of Africa was the worst in decades and affected the food security of millions of people.
• They travel up to 150 km a day riding the winds, and plagues are now tracked with satellites and weather models coordinated by the FAO.
• It appears in the Book of Exodus as the eighth plague of Egypt, and locust invasions have been documented for millennia.

Skeleton type

Invertebrate - chitin exoskeleton (insect)

Habitat and environment

Arid and semi-arid areas of Africa, the Middle East and southern Asia

Birth weight

The first-instar nymph weighs about 20 mg and reaches close to 1.5 g by the middle of the fifth instar

Sexual maturity

After the final moult the adult needs 2 to 4 weeks to reach sexual maturity depending on temperature and food; 2 to 5 generations are produced a year

Gestation / incubation

The eggs hatch in about two weeks; gregarious nymphs go through five instars and solitary ones through six, with nymphal development of roughly a month

Litter / clutch size

Solitary females lay 60 to 80 eggs per egg pod and gregarious ones 40 to 60; the pods are buried 4 to 15 cm deep in damp soil

Sources consulted: https://es.wikipedia.org/wiki/Schistocerca_gregaria; Hebrew University of Jerusalem; HopperWiki, ficha Desert locust; ScienceDirect (Hughes 1989); Science Advances, How colonial animals evolve; Wikipedia, Zooid; Hebrew University of Jerusalem, ficha Schistocerca gregaria; Schmidt 1994, Journal of Applied Entomology; fichas de especie; Bijlmakers, ficha Schistocerca gregaria; manuales FAO de identificacion; Manuales FAO de identificacion de la langosta del desierto

Best time: Breeding is triggered by desert rains, when ephemeral green vegetation appears; the swarms fly by day and settle to roost in the vegetation at dusk