Puzzling failure of Lepidoptera to sequester chlorophyll for colouration
(writing in progress)
There is an anomaly hiding in plain sight in butterflies and moths.
Most caterpillars eat greenstuff, which is green owing to the pigment chlorophyll.
Many caterpillars sequester the toxins of their food-plants, using these toxins for their own defence. This sequestration (which is the basic reason why many diurnal lepidopterans are aposematic) is remarkable for two reasons.
Firstly, the animal tolerates accumulation of toxins within its body, somehow avoiding harm.
Secondly, these toxins remain even into the imago (adult, reproductive) stage. This is surprising, given that in the pupal (chrysalis) stage the whole body ‘melts down’ into a mush and is reformulated virtually from scratch. Do the toxins not interfere with this ‘rebirth’ of the whole body?
Given the extreme ability of lepidopterans to preserve the toxins of their food-plants in their own bodies, it would seem like a small ask for them to do the same in the case of the chlorophyll so abundant in their food. And yet as far as I know this is NEVER the case. It was of course mooted initially by biologists, but as far as I know has been disproved every time it was investigated.
Green is a common colour in certain taxa of caterpillars. However, the green is, as far as I know, never of chlorophyll.
In the imago stage, green is a REMARKABLY RARE colour among butterflies or moths, much as it is among mammals. This is surprising for various reasons, but my point is that not only does chlorophyll not reach the adult stage of these insects, even the colour of chlorophyll is exceptional in the winged forms.
Which leads to the following question: just what is it about chlorophyll that makes it so hard, or so undesirable, to sequester in animal tissues?
(writing in progress)
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