Maggots on patio

We got a new patio put in last summer and notice that anytime it rains, the patio is covered in maggot-like larvae. I don't think they're fly maggots as they're longer and darker so maybe some other type of pupae or insect?

When it's not raining, there tends to be a couple along the cement between each slab so I guess when it rains, they are coming up from underneath.

There must be about seven hundred out there now as there are about 10 per slab.

Does anyone know what they are or how to blitz them? I assume the patio guys didn't bury anyone in the foundations :O)

Have no idea what type of insect these are, but you could try a fairly eco-friendly solution and use boiling water to kill them off. Are the joins between the slabs not sealed?

Are the Sparrows not taking care of them?