With GNU awk:
echo abbc | awk '{ print gensub(/a(b*)c/, "Here are bees: \\1", "g", $1);}'
See manual here to see the difference between gsub and gensub
gensub() provides an additional feature that is not available in sub()
or gsub(): the ability to specify components of a regexp in the
replacement text. This is done by using parentheses in the regexp to
mark the components and then specifying ‘\N’ in the replacement text,
where N is a digit from 1 to 9.