Cool weather adaptation??

[Lyril]

I've never had as many caterpillars/butterflies as this year (I took much better care of the plants). Last week I gave 227 chrysalises to Melbourne Zoo which has a magnificent butterfly house, so they would have a chance of flying before dying. But I still have so many caterpillars of all sizes on my plants, mature ones hanging in weird positions, and emerging butterflies.

The weather has been abominable for the last 2 weeks. Today was mild,
up to 17C (about 62F), down to about 5C (about 22F) and no frosts yet. Daylight is about 10.40 hours. Yet this afternoon I saw two new butterflies mating!

I read recently on the Monarchwatch webpage that butterflies need 13 hours of daylight to breed. These are still breeding in 10 hours, and in cool temperatures.

Is it possible for them to adapt to cooler temperatures? Every year I hope that some may survive winter but none have yet. Is there any chance that some may, - or are they all doomed? I've tried letting big caterpillars at the wandering/searching stage go in among long dry grass just in case they might find a place to survive winter.

Is this all a waste of time? What happens in Canada, or New Zealand when the temperature and daylight hours plummet?

[harpo787]

NOTE: I am no expert by any stretch of the imagination.

I believe I've read on here that monarchs during the winter "cycle" live a bit longer than the others. I assume that they are waiting for the break in winter.

But what the heck do I know? I'm in Florida where the winter might last a week before the temperatures climb back up. Then we'll get another couple of days of a "cold snap" and then right back up.

Can anyone else out there confirm/deny my thoughts on the intial topic?

[Sarah]

There are some butterflies that emerge during the very beginning of the migration that won't migrate. We aren't quite sure why they don't do so, but some will stay in the area and be reproductive. However, the caterpillars that result from these pairings won't survive the winter. Chip has written several articles about degree days (the amount of time needed to develop from egg to reproductive adult) in the Monarch Watch monthly email Updates. (You can find the index here
http://www.monarchwatch.org/update/index.html) Often, he will mention partial generations. For example, he might say the degree days in Michigan will give the monarchs enough time to go through 2 1/2 generations. That half generation is the group of caterpillars/pupae that aren't able to develop into adult butterflies. The butterflies that do emerge very late often won't reproduce; they won't receive the light and temperature cues to do so.

Monarchs are not freeze tolerant, so they won't be able to stick around and tough out the winter. It is highly unlikely they can adapt to cold temperatures. The monarchs that survived the extreme cold, wet weather at the overwintering spots in 2002 and 2004 did so because they were in the middle of masses of monarchs, not because they were genetically a bit different and were able to tolerate the cold, wet weather. In other words, the butterflies at the edges of the clusters were no different from those deep inside the mass of monarchs. (Except, perhaps, that they were unlucky in their position in the cluster!)

So, to sum it all up: monarchs cannot overwinter in places that consistently get freezing temperatures. The very late butterflies won't mate - it's not warm enough and they don't have the light cues - and often the last generation is incomplete. Sometimes these butterflies do last a bit longer because of the cool temperatures; they are not as active as those in the summer and do not expend as much energy. (This is actually one of the reasons the butterflies live so long at the overwintering sites. The temperatures in Mexico usually don't dip below freezing, but they are just barely warm enough for the butterflies to fly (generally 55 degrees F or warmer), so they mostly rest in clusters.)

Whew! I hope this explains things a bit!
Sarah

[Lyril]

I guess I was just hoping! It is now quite cold here but no frosts yet, and there are still some caterpillars on my plants. However most don't pupate properly and die during the process. I have 8 butterflies hanging off a curtain inside, being fed on nectar. None can fly properly but they've lasted two weeks now. And I've found some quite small caterpillars, about 1cm long. However when I bring them inside they don't seem to eat.
I guess Nature is profligate:these are all surplus to requirements!