Have you noticed the grubs act like they've rolled over on their backs? And have you noticed a problem with adult beetles of any kind around your property...maybe in the spring? Please place a coin in the picture so that we can better judge the size. And finally, where is your general location?

I'm sure that the exterminator loves the income, but spraying pesticides all over the inside and outside of the garage is not likely to help. Having a little bit of an idea of what kind of beetle this is would be helpful. If you're finding these grubs in the garage, you can be sure that they are coming from the lawn or garden.

OK, Yosale, I'll tell you a little story and see if you can relate: I have a compost bin in my backyard. Every year, the big green fruit beetles (Cotinis mutabilis) lay their eggs in the compost, resulting in a bumper crop of large grubs very similar to your photo. They are excellent decomposers, and quickly process whatever is in my bin. And sometimes, when they've run out of stuff to eat in there, they leave the box and wander the yard and across the patio in search of food (which would be anywhere they could burrow and eat what's under the soil). And this just happens to be the time of year that I find grubs all over my patio, stranded in corners here and there, and even stuck in some low-lying spider webs.

Do you have a compost bin, or perhaps just a cultivated area with good soil, near your garage? Maybe you are experiencing a similar kind of thing. Can't say for sure what kind of beetle grub you have, because many scarab grubs look similar, and I don't know where you live.

Here is a link that might be useful: Cotinis mutabilis