Someone just PM'd me saying I know more about butterflies than gnats. I assume this was a tactful way of suggesting I change the topic. So I will.
It happens that I do know more about butterflies than I do about gnats ... even tho I am learning to love gnats.
The big mystery about butterflies is how they manage to transmit navigational information to their offspring so they can make that awesome trek from Canada to a small mountainous region in Central Mexico [then back again] every year.
Some time ago, I read that a researcher found something in a butterfly's brain which might pick up the magnetic field of the earth.
This metallic-like substance might allow a butterfly to "read" the terrain it is traversing.
But, even so, how does that "map" get transmitted to the offspring? It takes about 7 generations of Monarch butterflies to complete a single migration.
Somehow, each new generation is born with "the map".
How is that possible, especially when you consider that each new butterfly must have the complete map even tho that butterfly can only make a fraction of the complete journey?
Does anyone know more about this mystery?
Thank you WWh for posting this, it is along the lines of what I understood about monarch migration.
Unless I'm reading Bill's link wrong, it seems to contradict grapho's assertion that the Monarchs don't make the entire migration journey. If they don't, tagging them would be useless - or am I missing something?
>>make the entire journey<<
Yes, the article states explicitly that they do -- roundtrip. I wonder what on Earth they tag them with. Also, I thought butterflies didn't eat (after molting); if so, how do they have the energy for to fly nearly 3,000 miles?
Re: Do migrating butterflies make the entire journey?
Answer here [on "Journey North" website]:
Q. How long do adult Monarchs live?
A. This depends on when they live (summer or winter). It also varies a lot among individuals (just like it does it humans). In the summer, adults live from 2 to 6 weeks in captivity, and probably about that long in the wild. The ones that migrate live longer, from August or September to about April (although a lot die before this). When people hear this, they say they'd rather be a migratory monarchs, but these butterflies probably face many more risks, and are likely to have a smaller chance of getting offspring into the next generation."
I guess I don't know as much about butterflies as I thought?
Still, it remains a mystery to me how a butterfly can be born with a "map" in its tiny brain which will guide it from Canada to a very small region in Central Mexico.
It's easier to understand how migrating geese navigate. They are responding to light cues. This isn't what cues in Monarch butterflies.
Gnats are harder to love, but easier to understand.
i haven't had a chnace to read to read Dr Bill's link.. but i recently read Prey--Michael Critions book about nano machines that escaped to the wild, and how they were programed.
the small amount of magnetic material might be the clue.
at some point (temperature, but more likely shorter day light hours) monarchs start to migrate to longer days. (ie south. )
as they do, they pass through some (many?) magnetic anomalies.. and each one activated the magnetic material in their brains. eventually (some what by luck, some what by geograpy (monarchs don't like flying over large bodies of water) they find them selfs in texas (moving south and west (opposite their north east spring migration (again, why west? programed to fly to longer days, and setting sun? (and in spring longer days and rising sun?)
flying further south from texas puts them in the gulf.. and they don't like flying over water.. so they continue west, (and south.. and suddenly-- they are sensing a specific magnetic anomoly--one their brains calls 'home')
since all you have to do is have programs that say:
Fly north and east so long as there are X or more hours of daylight (and of course the further north they get, the longer the day)
When there are fewer than X hours of daylight fly south and west. (east and west being driven by the sun rise/set) Avoid large bodies of water.
If you encounter this specific magnetic field, home towards it.
pretty simple, the program can be instinctual, and pass from generation to gereration with out the need for a big brain, or for maps. and it would work.
(not anyless beautiful for being understandable. )