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Color Variant--mutation? Probably not.

I noticed an unusual off-white caterpillar on a fennel plant in the back yard a week or so ago. It was very small (~1/2") and looked like it had just shed its skin, so I assumed its light color was related to the recent shedding and that it'd darken in a few hours. I brought it indoors to join the rest of the group.

But the next day, it was still a very light color. Odd.

The two images below were snapped after a week of growing and munching on fennel.

Without looking at the 2nd image, see if you can spot the oddball caterpillar in the 1st image just below. He/she is now more than an inch long.

The intention is to watch what happens to this guy as he/she grows and sheds and pupates and then emerges--will the butterfly have unusual coloration too??

Suspense! This is an inevitable part of indoor caterpillar/butterfly management.

What might cause this lack of pigment? A mutation in a gene that affects pigment production? Actually, black and yellow pigments are being produced, although there is far less black pigment than usual.

Here's a closer look:

More pics to come as this guy grows and develops.

Two days later: During two days of sitting quietly, he/she has changed quite a bit:

Notice the increase in normal coloration--lots more black than before.

New hypothesis: an earlier-than-usual molt to the 1st "greenie" instar, before the normal pigmentation had had a chance to develop. The catch-up is happening now.

After another 2-3 days, it appears that the above is about as much catch-up as is going to happen. The image belows shows the caterpillar next to cats with normal coloration. It looks like we just have a less-pigmented variant on our hands here.

This guy is now close to the roamer stage of development.

No roaming! Surprise--this lazy fellow decided to just attach him/herself to a fennel stem and be done with it.

Notice the thick layer of silk deposited all along the stem, binding the harness and the tail.


Betting this will be a green (rather than tan or brown) pupa...

And so it is:

Upshot: the butterfly that emerged had normal coloration.