I was lucky enough to find and observe a mating pair recently ^_^
Stalk-eye Flies, as the name suggest, have very long eye-stalks (yes, those are the eyes on the far left and right :p).
The males (on top) tend to have much longer eye stalks, which acts as a prerequisite to "tackle" the females (bottom).
Males and females tend to rub their forelegs together (also in my Flickr account), which I suspect it to be a mode for stridulation- calling out for a mate.
When a pair of male and female are close together, the male will bend its body low while using its forelegs to continuously tap the surface of the leaf as a sign for mating.
When mating, the male steps on top of the female. The forelegs of the male are put on the "V-shaped" abdominal spines of the female (so that's what its for lol :p)
PS: These flies are a nightmare to photograph up-close due to their very weird body shape!
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