It's an interesting conversation that, unfortunately, is based around a big myth perpetrated by laymen-women every day. I was talking to a friend of mine the other day who's helping with some research on one of the Pacific rattlers over in Oregon, and we got onto the subject of ontogenic changes because we were talking about my black milks. Ontogenic changes, for those of you who are unfamiliar, are usually relatively rapid, obvious visible changes that occur generally from an animal's "teenage" time until its maturity. Two good examples of this are emerald tree boas and green tree pythons (which are also two good examples of convergent evolution, but I digress), which are each born bright red or yellow, and change to green over the next year or two. Black milks do something similar, being born as a tricolor and changing to pitch black adults. Well anyway, the conversation delved into venoms, and he said he was pretty sure he had read something about some venomous species who undergo an ontogenic change in their venom components. This would make total sense with species who feed on a certain prey item as a baby and then switch to something different, for reasons such as size and availability, as adults. The only one that comes to mind for me, though I'm sure there are others, are death adders (Acanthopis ssp.). Baby and juvenile death adders feed almost solely on baby ground skinks, but adults take a variety of prey, including mammals. I would be curious to see if any of the components change as the animals mature.
Anyway, I just wanted to shed a little scientific light on a topic usually discussed by rednecks while justifying to themselves why they just killed that "baby copperhead" (i.e., baby water snake, adult ringneck, adult earth snake, goes on [img]ad nauseum[/img]).