National Geographic Interactive - 02.2020

Flying swarm

Flying adult

2.5-5 months

Nonflying

nymph

24-95 days

Egg

10-65 days

MAJOR

LIFE CYCLE

STAGES

relative size

SOLITARY

NYMPH

actual size

CNS

Brain

SIGHT &

SMELL

TOUCH Thoracic ganglia

serotonin

released

Nerve

Sensory

neuron

Dendrite

Signal

to CNS

FEMUR

FOOT Hair

EXPLORE | DECODER

An unintentional gathering

Always in search of food, solitary

locusts are forced together during

dry spells, when vegetation dies

off and leaves minimal areas of

green within the desert.

Sudden transformation

Within hours of crowding, a boost of

serotonin in the central nervous system

(CNS) spurs behavioral changes such as

rapid movements, sociability, increased

self-grooming, and a more varied appetite.

1

2

The release of serotonin is

caused by stimulation of the

leg hairs, as well as the sight

and smell of other locusts.

BY TAYLOR MAGGIACOMO

HOW TO SET OFF A

PLAGUE OF LOCUSTS

VISUALIZE A SWARM of 70 billion flying insects, covering 460 square miles—

about 1.5 times the size of New York City—and devouring more than 300

million pounds of crops in one day. That’s how big a single swarm can get.

Plagues, made up of multiple swarms, are referenced in the Bible and the

Quran. Of the thousands of grasshopper species, only 22 can be described as

locusts. They’re distinguished by their ability to transform from a solitary

state—actively avoiding other locusts—into a social, or “gregarious,” state

in which masses of them darken the sky, ravage the land, and terrorize

inhabitants. In 2004 a million Malians faced famine after locusts consumed

90 percent of their country’s cereal crops. Changes in locusts’ behaviors

and physical traits can eventually be reversed if locusts get isolated, or

they can persist and be passed on to offspring. —KAYA LEE BERNE

Preventing a plague

Weather patterns and histori-

cal locust records help experts

predict where swarms might

form. Once identified, an area

is sprayed with chemicals to kill

locusts before they can gather.

28 NATIONAL GEOGRAPHIC