Part one: tie the knot and get married.
The bottom line is: get married and be a good couple.
The katydid is the katydid now, and the vibration is the vibration of the wings. The fifth book, Nan Zhou Katz, comes from Nan Zhou, a realistic poetry collection in The Book of Songs. It means to congratulate many descendants, handed down from generation to generation, family prosperity, harmony and joy.
Melon is a big melon, not a small melon. Melon means that it is always small at first, but its vines will grow and reproduce. It is the name of an auspicious picture that wishes future generations prosperity.
The general moral is that people are prosperous and their children are full.