help! grep -r -i "aaa" *.f90 does not do what I want

[bsmile]

I hope it can recursively look for aaa in all *.f90 files in all the subsequent directories, but it complains

grep: *.f90: No such file or directory

Any idea why this happens? Thanks,

[Rubberman]

Do this instead:

find . -type f -iname '*.f90' -exec grep --with-filename -i "aaa" {} \;