Tony T wrote:

Need a photo of a Rhagoletis from behind:D
According to Marshall "the wing-banding pattern....seen from behind.. makes the fly look remarkedly like a jumping spider (the bands look like spider legs)"
Who wants to tangle with a jumping spider?

Edit: Further reading indicates that the mimicry is to fool jumping spiders as these spiders are the major predators. "Greene et al. (1987) and Whitman et al. (1988) showed that Z. vittigera mimics jumping spiders and is significantly protected from these common predators on its host plant. During the fly's wing flicking displays, its wing pattern resembles the legs and the abdominal spots the eyes of a spider in its own territorial display."

See: Reference here