Here is a picture, it's dark and rainy today so I had to hold a flashlight on him. I'll try to get one tomorrow of it next to another for comparison.

Here is a link that might be useful: {{gwi:510089}}

Has the caterpillar been subject to cold weather lately?

Well, it was very cool last week, but this is one I brought in as an egg and it's been in the garage the whole time. Not as cold as outside,but it was very cool last week at night. No others are like it! I'm hoping it will be a HUGE monarch. :)

Some are just darker than others. I had a really dark monarch cat last year - see it {{gwi:510090}} Cool looking, but he turned out to be a regular beautiful monarch...nothing 'special'. "Missherry" told me he was just "melanic", which means dark coloration.

Melanin is also a defense mechanism. So, if the cat was exposed to something, it is possible to be darker. Most likely it is a genetic thing. FYI;

Abstract

Annals of the Entomological Society of America 96(3):211-216. 2003
doi: 10.1603/0013-8746(2003)096[0211:TVILCI]2.0.CO;2

Temperature-induced Variation in Larval Coloration in Danaus plexippus (Lepidoptera: Nymphalidae)
Michelle J. Solenskyac and Elizabeth Larkinbc

a wats0094@tc.umn.edu

bCurrent Address: University of Notre Dame, South Bend, IN 46556

cDepartment of Ecology, Evolution and Behavior, University of Minnesota, 1987 Upper Buford Circle, St. Paul, MN 55108

Color variation has been reported within many species of Lepidoptera, and may be important in larval thermoregulation. Researchers have reported seasonal melanization and lack of yellow pigmentation in monarch larvae (Danaus plexippus L.). While the latter results from a recessive autosomal mutation, the source of variation in larval melanization is unclear. We measured the proportion of black, white, and yellow coloration on monarch fifth instars when larvae were reared in warm (32Â22°C), control (27Â17°C), or cold (20Â10°C) temperature treatments. We found that temperature had a significant effect on monarch larval coloration. Larvae reared in a cold environment had more black and less white and yellow pigment than those reared in a warm environment. Because coloration affects absorption of radiant energy, color variation in response to temperature may be an ectothermic adaptation to suboptimal thermal conditions.

-Elisabeth

Thanks Elisabeth! very interesting!

FWIW...

The single odd colored larva in this case is probably just a pigmentation mutant (or throwback), and that color variance is not likely to have any effect on the outward appearance of the adult Monarch.

Melanism is common in many species in the arctic and higher alpine habitats (cold climate habitates), not only in the larval stage sometimes but mostly as adults. This occurs not in just a few individuals, but in entire colonies of a species in these habitats. So in these colonies it is a genetic adaptation that evolved over eons of time and is now a dominant instead of a recessive gene in their DNA. With the adults the females especially are much darker, which is thought to help them absorb radient heat better for egg production.

Melanistic abberations (and other color/genetic morphs) in the adult stage are normally developed in the pupal stage (after histolysis and during histogenesis). They are fairly easy to induce in the lab if you know the mechanics for a given species. For a few years I experimented with several alpine species creating abberations to better understand how the environment can artificially control complex metamorphosis to the point that it stimulates evolution.

L.

Yes it seems that sometimes they are just darker. In my (limited) experience I've seen more darker ones during the winter (they can absorb more heat from the sun when they are darker so I can see why), but had one that got bitten by an ant.

He was about the blackest one I've seen (below), to the point that I seperated him from the herd in case he was diseased. The ant remained attached to him (you can see it if you look closely on his head - little brown spot) until he pupated. I tried to pull it off but it would not budge and I feared damaging the cat further. Anyway he came out as a perfect butterfly so was an interesting study.

{{gwi:510091}}

Wow! That's REALLY a dark colored monarch cat!
Sherry

Yes Sherry you can understand why I thought he was sick!!

WEED30---that's not a monarch cat pic you posted, that's a swallowtail caterpillar, LOL!!! If a monarch emerged from it that would be miraculous. Anyway, it's a beautiful specimen!

Oh geez, you're right! Well, he was really dark for a BST!

It sure looks like a Monarch to me! I've raised a lot over the past few years and some of mine were darker than the rest. I have a pic that I took of some color variations last year and will post it. I just wish I'd have also had a really light Monarch at the time to put in that pic. Sometimes I'll get one that's mostly all yellow. That is milkweed that yours is on, right? If you've seen it eat the milkweed, it can't be any other butterfly cat in your area but a Monarch. Even if it weren't milkweed, I'd say it's a Monarch and it's crawling around finding a place to pupate, but it looks like Tropical Milkweed to me.
Cathy

Here's the pic I was talking about:
{{gwi:510005}}

Wow Cathy, that's a fantastic shot!

I'm still waiting to find one of these guys.

Me too KC. Me too!! I have been overrun with Monarch cats these past few weeks, and not a one of them looks unusual. :o)

I had these darker ones also and they turn out to be just a normal Monarch.

Here's another one...happy ending here too.

{{gwi:510092}}

I have a cat now with wider than usual black stripes - wondering if it is a male...