Wednesday, July 3, 2013

Blue-tipped Dancer

Female Blue-tipped Dancers come in brown (first photo) and blue (second photo) phases. Note the blue tip to their abdomens and, in the blue form, the azure triangle at the rear of the black side stripe. Why do the females come in different morphs? In some damselflies, some females look like males (andromorphs), apparently to reduce male aggression towards them. But, in the case of Blue-tipped Dancers, neither morph looks like the male. One hypotheses is that the two morphs suffer different reproductive and predation rates. If one morph has a high reproduction rate but is often taken by predators, a second morph, with lower reproduction, but less likely to die from predation, may result in both morphs coexisting.
Males (final photo) are a little easier to identify—they are the only dancers with violet, black, and white thoraxes. Notice the male in the last photo is munching on a winged insect. Why don’t males come in two morphs? Scientists suspect that the females are more exposed to predation than their mates (Cordoba Aguilar), thus giving them added advantage to being polymorphic.

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