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Wednesday, 5 December 2018

Complicated Genetics

Think of the complicated genetics involved in this example.

Click on the photo to enlarge

This is the SAME individual katydid from just after hatching to adult.
As a first instar nymph (fresh out of the egg) the little katydid behaves much as an ant or a wasp. The antennae flicker when it moves in a wasp-like fashion and its movements are jerky.

After a few moults the same katydid looks quite different. Note the difference in colour pattern and also the antennal colour is entirely black and does not have the white patch near the base of the antenna as is seen on the first instar.


Remember, this is the same individual katydid as in the first frame. This is in its last instar stage, just before it moults into the adult. Almost everything about it is different and its behaviour is in now way wasp-like. The colour and pattern on the legs is different and there is not much suggestion of the black colour as seen in the early instars. Note the slightly separated wing pads. This indicates that the individual is about to moult into its adult stage.

The adult! It's hard to imagine that this is the same individual at in the first frame after a few weeks time. Most of the intense colours are gone. Only traces of orange can be seen on the forelegs and the head. It continues its life amongst leaves and foliage of rainforest trees. This species bears a characteristic short black stripe on base of the dorsal pair of wings (tegmina). There are also a few scattered small dark spots on the tegmina.

So are there explanations for this scenario. It's diverse changes are not just happenstance in my opinion. The wasp-like or ant-like appearance and behaviour of the first instar may help it avoid being predated upon by lizards and birds when it is on the ground or on tree trunks. The mid instar appearance might be protective in the sense that it appears more like a piece of bark or leaf litter than an edible katydid. At this stage its movements are jerky and wasp-like. Later instars are probably on leaves during the day and the green colours and patterns conceal it. The adult is not unlike any of the more than 10 species of the Phaneropterinae that occur with it. The katydids are nocturnal and spend their time in foliage. They are vegetarians.

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