Mayfly Chair Black. The Mayfly Chair is a hybrid of the lightweight Monarch and Mantis Chairs, boasting both rockability and stability. This doubled functionality is granted by its dual-structure design. The main structure is a modified Monarch frame, which can stand by itself as a balancing two-legged chair for uneven ground. The secondary structure is a removable front foot that can easily attach and detach to the main frame, giving it the stability of a standard chair whenever you please.