What is the title of a classic black and white horror film where space pod unearthed in tunnel being dug for new subway examination reveals grasshopper type insect?

The classic black and white horror film you are describing is "The Thing That Couldn't Die" (1958).

In this film, a tunnel being dug for a new subway in New York City unearths a mysterious space pod. Inside, they find a preserved, ancient creature that resembles a grasshopper. This creature, though seemingly dead, possesses a powerful, regenerative force and brings terror to the city.