However refined and decadent the styles of 18th century gentry, they idealised the life of shepherds in its simpleness, inventing a kind of romantic antidote to the highly formalised life of high society. There were parties where they acted out their romantic ideas of the part, dressing up in rurally inspired dresses (silk of course) with aprons (with lace of course).
Part of this masquerade is the bergère, a flat, wide-brimmed straw hat, usually decorated with flowers and ribbons. Mind you, it was not only worn for shepherdess masquerade - that's only where it probably originated - but for any summer outdoors activities. Sometimes they were covered all over with pinked ruffles of silk. From the mid 17th century until the advent of the huge hats of the latter decades of the 18th, it is the only kind of hat worn by women. Apart from it, the head was, if at all, covered with a fontange, bonnet or hood.
French shepherdess costume (no bergère)
English version (with bergère)
The hat only