Buckeye Observation - Junonia coenia

Thanks For Valuable Inputs

I found an excellent explanation of the mechanisms contributing to seasonal polyphenism on Developmental Biology website. Both cabbages & buckeyes are exemplified, stating, Day length and temperature are the major environmental determinants of the polyphenism. The reproductively active summer form can be induced experimentally by long day length and higher temperatures, and the diapausing autumn morph can be induced by shorter day length and lower temperatures.

I had suspected that day length may be a contributing factor, as I was raised in the nursery business. You have to trick Easter lilies in to blooming the week before Easter by covering with black sheets or by leaving lights on at night, thereby adjusting the length of day.

… Robert Lord Zimlich, 21 October, 2009 - 7:54am

Cabbages, too

Maybe this explains why, partway through summer, the garden had butterflies that looked like cabbage butterflies but were smaller. I thought they were a different species. Possibly they were a seasonal variation.

… G Whiz, 20 October, 2009 - 2:12pm

Some early and late season bu

Some early and late season butterflies up here in NY are smaller than the summer broods. In particular, I have noticed small Common Buckeyes late in the year. It may have something to do with body size/area. Less heat is needed to take care of a smaller insect when the air temperature is colder.

… Rich Kelly, 20 October, 2009 - 1:43pm

Wondered About The Cold

Last winter, I noticed several buckeyes tucked away in one of my woodpiles, like letters in mail slots. If the impending cold weather is the cause of smaller broods, what is the mechanism? Length of daylight hours would seem most likely candidate. Reduce their metabolism or simply reduce their eating time? Interesting.

BTW I don't disturb that woodpile because a rabbit family also lives under it.

… Robert Lord Zimlich, 20 October, 2009 - 2:48pm

I don't know what the mechani

I don't know what the mechanism is. There's a famous narural history principle (I can't remember the name) that states that for any one organism (ignoring multiple broods in butterflies) that latitude/elevation have a direct effect on body size. I don't remember if farther north meant larger or smaller (if larger, then my prior comment may have been wrong). But this may have to do with animals that live during the summer. A large wing surface could absorb more sunlight??? Maybe Harry Z. or somebody else can clarify this.

… Rich Kelly, 20 October, 2009 - 3:12pm

Is it something like seasonal polyphenism?

And some other thoughts:

Seems to me like with the cooler conditions:

-There's more wind- Smaller wing and body size would offer better resistance to the wind.

-The smaller body size could allow the butterfly to warm up a little quicker than normal. (Maybe even have some special adaptations to warm up more quickly). (Think thermal capacity)

… Andrew Meeds, 20 October, 2009 - 4:00pm

Size and temperature

A smaller animal would be less good at conserving heat, just as a cup of soup cools faster at room temperature than a big pot of soup. It's that surface-to-volume thing.

… G Whiz, 20 October, 2009 - 5:28pm

Conserving heat/Heating up are two different things

The smaller cup of soup would also heat up faster. That's what I was going for- Quickly increasing temperature rather than conserving the temperature- Although, it would make sense that there might be some species that get larger with seasonal polyphenism for that reason.

… Andrew Meeds, 20 October, 2009 - 5:38pm