The constellations march ever westward from month to month, with old ones disappearing into the sunset as new ones rise in the east.
This is because the stars run like clockwork on a specific schedule. Thanks to the fact that our Earth rotates on its axis once every 23 hours and 56 minutes, a star — any star — rises and sets four minutes earlier every day than it did the day before. This motion means that any given array of constellations will appear in the same location of the sky two hours earlier each month. So, the celestial scene you witnessed by staying up until 11 p.m. in mid-April is already there at dusk in mid-May.
