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Ants and Passion Vines

Any ideas what the yellow dots are on this Passiflora leaf? Are insects involved?

passionvine-leaf

It turns out that insects are part of the story, but probably not in the way that you might think.

heliconius-caterpillar

This is one of the insect characters, the larva of a Heliconius butterfly. The female butterfly lays yellow eggs on passion vine plants, mostly in the tropics. The larvae consume a great deal of the plant before pupating.

heliconius-butterfly

In Arizona, another species can wipe out passion vines.

fritillary-caterpillar

This is the larva of the gulf fritillary butterfly, Agraulis vanillae.

Researchers have shown the yellow spots on the leaves are made by the plants as a defense against these butterflies. When the butterflies lay eggs, they avoid laying on plants where another female has already deposited eggs. The yellow spots mimic eggs and thus fool the butterflies into going elsewhere.

That is only part of the story, however, because the yellow spots serve another purpose. Those are nectaries, glands that produce nectar. The free source of food attracts ants, which in turn defend the plant against any butterfly larvae that do hatch.

I have to say that at first glance the plant fooled me too. Did it fool you? Did you think those were insect eggs?

The theme today for Life Photo Meme at Adventures of a Free Range Urban Primate blog is "honor an invertebrate." Why not ants that protect plants?

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