I have always been curious of this. Why are Lepidoptera larvae so specific to a certain host plant?
Surely they can't be so fussy, that they would rather die than eat the leaf of another plant. I imagine there must be some sort of connection between the larvae and the chemical composition of the plant's leafs? (E.g. Papilio species require citric acid?)
Post by Adam Cotton on Jan 30, 2012 10:39:12 GMT -8
Not all Lepidoptera larvae are specific to a single hostplant, many commoner species can feed on a whole range of species, often related, but other species (particularly certain moth pests) can eat just about anything.
You are correct that there is a connection between the larvae and chemical composition of the plant's leaves. Most larvae need to receive a certain chemical stimulus to initiate feeding, otherwise they will just starve to death.
i think that if you look at many species of butterflies that eat allot of different species of plants, they in turn end up being more common. im from New Zealand. and here Pieris rapae the common white butterfly stands true to its name.. its everywhere here, and its larvae eats a whole range of different foodplants. take our beautiful vanessa gonerilla red admiral on the other hand, its quite rare these days..and feeds only on stinging nettle. now people remove stinging nettle because its a weed nobody likes very much. and ofcource its hard for the butterflies to find and reproduce. Now just like the common white butterfly i mention earlier, if every butterfly ate the same plant, or more types atleast, the more butterflies that would produce, the more butterflies the more problem...it would totally put out of balance the laws of nature and the big reason why most species have only 1 type of plant. it just keeps eveything in balance. like the water cycle, keeps on a constant chain reaction;)
This basic question helped lay one of the corner stones of coevolutionary theory (interestingly - the other main thrust of coevolution was also laid down by a lepidopterist - Dan Janzen - although he was not working with leps at the time.
Here is the original paper. As I recall, there was a much more readable version in Scientific American -