Answers From The Monarch Butterfly Expert, Part II
Julie BrophyTo: Journey North
From: Karen Oberhauser
From: NEW YORK
A. The monarch stores a poison called a "cardiac glycoside" that it gets from the plants it eats. This poison is similar to digitalis, which can be used to help people with heart problems, but can kill people if they consume too much of it. The potency of monarchs depends on the potency of the plants they ate when they were caterpillars. Some kinds of milkweed have higher levels of cardiac glycosides than others.
Q. Why do morarch's migrate and not hibernate? from: Deanna Jones
A. This is an excellent question! For some reason, monarchs have just not evolved to hibernate. Most other temperate insects can withstand the freezing temperatures of winter by entering a state called "diapause." Some do this as eggs, others as larvae, pupae or adults. Many people think that monarchs evolved in the tropics, and just move north each spring to take advantage of all the summer milkweed we have in places like New York and Minnesota, where you and I live.
Q. If monarchs did hibernate, how much food would they have to eat in order to survive the winter? from: Deanna Jones
A. Since they are cold-blooded, they wouldn't actually need very much,
because they wouldn't be using up energy during the cold winter. They
need more energy to migrate and overwinter than they'd need to overwinter
in a cold climate. This means that it's not energy considerations that
make them leave, just an inability to withstand very cold temperatures.
A. We don't know for sure why they go where they do. In fact, some may actually go to Arizona, and some people think that in some years monarchs from the overwintering colonies in Mexico may vear west and end up in the western population.
There are so many unanswered questions about monarch migration, that it will take many many scientists years to answer them all!
Q. Is there any difference between chrysalid and a chrysalis?
A. No, they're the same thing. Both of them mean the pupa stage of a
butterfly. I've always thought that people said 'chrysalid' because it's
easier to make this word into its plural form ('chrysalids'). I've never
known how to make 'chrysalis' plural, so I usually just say 'pupa' and
'pupae'! I think you should write a poem about all of these words!