what is this?

And just when you think it clear of debris, clean it again. When I had fenders off the car, I hosed the cowl down, used a hanger to loosen up the crud, air hose to blow all the stuff out then vacuumed it out. Put car back togehter. I was driving to a show 30 miles away had the air box open on a warm day. All of a sudden pass a semi going the other direction. I was doing 60 he was going at least 50. All of a sudden I was covered in stick leaves acorns and everything else. The crap was all over the car, under seat in the back dash covered me and went up my shorts too.
So now I drive with it open all the time so crap dont get built up again.