The sea locust was a small, herbivorous semi-aquatic lifeform native to the planet Kwejian. In addition to crawling on six insectoid limbs, it could also inflate a large dorsal sac and propel itself through the air with a whirling motion. When airborne, it emitted a blue glow from various parts of its body. Sea locusts normally lived in the ocean in massive swarms, communicating with each other through an electromagnetic connection.
In the late 31st century, the Burn shifted the orbit of Kwejian's moon. Consequently the planet's tides changed, causing vast numbers of sea locusts to emerge from the ocean and devour the Kwejian harvest. The starving Kwejian accepted a deal from the Emerald Chain, offering their trance worms in exchange for a repellent to keep the locusts at bay; though the Emerald Chain claimed the repellent was a humane means of control, it in fact poisoned the locusts. Kwejian scientists worked for years to find another way to move the locusts back out to sea, but their numbers were simply too great.
In 3189, Emerald Chain leader Osyraa withheld the repellent from the Kwejian so as to compel Kyheem to deliver his brother Cleveland Booker to her. The sea locusts once again entered the Sanctuary and began consuming the harvest, threatening another famine. After the crew of the USS Discovery forced Osyraa to retreat, they devised a means to amplify the locusts' electromagnetic connection, allowing Kyheem and Booker to combine their empathic abilities and persuade the swarm to return to the ocean. (DIS: "The Sanctuary")