One reason to visit the Damien Hirst retrospective at London’s Tate Modern is to meet the drunken butterflies. They are in a two-room installation entitled In and Out of Love. In its first room you see a few dead butterflies randomly stuck onto a group of big canvases that have been gloss-painted yellow, purple, pink, and so on, like a jumble of xylophone keys. Then you pass through PVC curtains into a bright and humid gallery where dozens of live specimens, of tropical origin, woozily waft through the air. Their dark silhouettes, passing you by, flash iridescent blues, vermilions, and lime-greens.