Continuing on the theme of masquerade...

As promised here are some photos of that caterpillar that was peeking out in one of the photos in my last post. This is another Prepona sp. but I'm not sure which. I only found it because of the conspicuous frass pile collecting on a leaf underneath. What drew me to that tree though was the characteristic feeding damage from Prepona caterpillars. They chew off the first half of the leaf but leave the middle vein, then to that vein they silk small cut trimmings of that leaf to give it a "trashy" kind of look. During the smaller instars the caterpillars are usually seen dangling from the end of the vein in full sight, but they look so much like the other "trash" that you often miss them. The bigger ones will sit right on top of leaves or on branches. This one was dangling from a full dead leaf that had been silked to the branch. It was wrapped kind of in a spiral shape on that handing leaf. I showed it to several people and they didn’t see it even when they were inches away.

Prepona sp. (Nymphalidae)

Here is a smaller individual from the same plant (maybe a full sib). The first photo below shows the characteristic feeding damage.

It almost disappears once it gets amongst its "trash" on the leaf vein. In many ways masquerade is more similar to mimicry than crypsis. When people discuss crypsis as an anti-predator defence they usually mean that the predator does not detect the prey. It is perhaps more realistic to recognise that the predator does see the object it just doesn't think that that object is a meal. In classical Batesian mimicry theory, the number of mimics should be smaller than the number of models (model = the object being mimicked), otherwise predators don’t learn to avoid that type of prey. Biologists call this "frequency-dependence" because the efficacy of the defence depends on the relative frequency of the models to mimics. In theory this should be the case in masquerade too, it's just that the model is usually something incredibly common like a living/dead leaf or a twig.

On a night walk tonight I found another dead leaf mimic:

A colleague/friend recently blogged about The weird and wonderful world of katydids. I doubt that I could do a better job of enthusiastically describing these guys so I'll leave you to read his post. He writes very well and I highly recommend following his blog: Katatrepsis. He's right though, the detail of the false venation is mind-blowing.