Wood boring insect? Please sustain!...? I live in Michigan and I have be noticing small piles of...

I live in Michigan and I have be noticing small piles of sawdust under the steps on my deck. I looked and they give the impression of being to contain a little black squishy thing, looks resembling a raisin. I'm thinking larva? and whatever is boring makes a faultlessly round hole about the size of pinky fingernail on the bottom side of the step. I don't think it is termites and I don't see any live insects anywhere around the nouns. Any ideas??
Venus flytrap?
Answers:    guessing carpenter bees...they make a model 3 / 8 inch hole. At night shoot any type of insecticide into the hole. The usually attack unpainted lumber so make sure the underside of the lumber is also hermetically sealed or painted