I'd never heard of that belief so I did a little googling - makes for interesting reading!
It seems that in Africa the praying mantis is thought to bring good luck to whoever the mantis lands upon, and even thought to restore life to the dead. Bushmen of Africa believe the praying mantis is a divine messenger.
In Signs, Symbols & Omens: An Illustrated Guide to Magical & Spiritual Symbolism, written by Raymond Buckland (2003: 231), a Praying Mantis is regarded as a “very fortunate sign,” says Buckland.
...and a quote from another website
It seems that in Africa the praying mantis is thought to bring good luck to whoever the mantis lands upon, and even thought to restore life to the dead. Bushmen of Africa believe the praying mantis is a divine messenger.
In Signs, Symbols & Omens: An Illustrated Guide to Magical & Spiritual Symbolism, written by Raymond Buckland (2003: 231), a Praying Mantis is regarded as a “very fortunate sign,” says Buckland.
...and a quote from another website
..With its worshipful appearance on one hand and bloodthirsty behavior on the other, the praying mantis, widely distributed across the world, has given rise to many myths, as suggested by its very name, “mantis,” which means “prophet” or “seer,” a being with spiritual or mystical powers. The praying mantis supposedly directed pilgrims to Mecca, the holiest site in the Islamic world. It became a god, restored life, bestowed good luck, and helped find lost sheep and goats in Africa. It helped wandering lovers and lost children find their way home in France. Its eggs cured bedwetting in China. Its brown defensive liquid blinded men and killed horses and mules in the United States. In 1957, it even gave rise to The Deadly Mantis, a movie about a giant praying mantis entombed in the ice of the Arctic. The creature revived after lava from a volcanic eruption melted its frozen encasement. It headed southward, threatening to destroy both New York City and Washington, D. C....