Alessandro Dell’Acqua invented a new fashion category with his No. 21 show tonight: military rococo. A khaki shirt belted over a pencil skirt in swirling, ornately sequined macramé defined the idea. It wasn’t the only look that married opposites. “Disdain for convention” is, according to the press release for today’s show, a Dell’Acqua signature. Equally typical of the designer were this collection’s sheer lace looks worn with men’s shirting, the lingerie and pajama daywear, classic tartan turned see-through organza…all of it belted tightly together in combinations as unlikely as the bourgeois Milanese matron, uptight on the surface, rotten to the core, who is Dell’Acqua’s enduring inspiration. Folksy macramé will never be the same after its incarnation here, in a sparkling, decadently lurid green.