Interesting. How long were they pupating, i.e., undergoing metamorphosis as a pupa? I am most curious. Also, what were the conditions? Were all of the pupae left outdoors? Or, were the brought/raised indoors in a controlled climate (as far as temperature)? Was the humidity level different this year? Higher/lower?

One thing I've noticed here in Southern California is that when the temperature is very high, there is definitely a higher mortality and fewer making it through the life-cycle all the way to adulthood. The likelihood of a caterpillar contracting some horrendous bacterial or viral infection appears to be much higher due to the high temps and high humidity due to the foggy mornings/high temp afternoons. Moisture build-up is very high and trying to keep things dry is most difficult; thus, lessening the potential for mold/mildew/etc. is well, ARGH!

Thus far, this summer has been somewhat unusual. We have had some really hot days but at the same time, it hasn't been like previous summers. So far, of all the various species I've raised, I have had fewer casualties than usual. Of course, with regards to Monarchs, I am just beginning my 'big' fostering time right now so it will be interesting to see what happens. So far, so good, though. One pupated and that one is not perfect so it could be a sign of things to come. We shall see...it will be interesting to me, particularly in the next few days as the first 'group' pupate.

CalSherry aka tdogmom

PS/BTW: Did you check for Oe?

My first brood here in New England was late this year because of all the rain we had in June and July. Those monarchs did very well. I have my next brood in cat stage now. I found an egg yesterday and am heading to the cemetery today (it has a nice milkweed patch) and see if I can "rescue" any more eggs before Hurricane Bill's big winds decide to pass by us this weekend.

I raised & released 9 monarchs this summer, and one of these was a bit smaller than the rest, and seemed less capable of vigorous flight. I suspect that it was infected with Ophryocystis elektroscirrha, a parasite that lives in the scales of both monarch and queen butterflies. I believe that the spores can be seen with fairly low magnification, maybe 100x, but I have not actually done this yet. I have seen this pathogen described as a protozoan, and also as an oomycete. My understanding is that an infected female monarch will lay eggs that have spores visible on the surface, and that the monarch cat becomes infected when it eats the egg, after emerging. Therefore, if you could catch the little buggers just as they emerged from the egg, & somehow separate cat from egg, you might be able to prevent infection with Oe.

Thank you, Eric. We also live in Dane County; your explanation certainly seems to be the most logical explanation.

Really it could be lots of things but disease is the most likely culprit. Did you test for OE? This is really important. The later in the season, the higher the rates of this disease and what you are describing is typical for OE. See the link below.

The way OE works is that the spores build up on plant material in the wild. It also builds up in the rearing containers of those of us who raise monarchs. So, as the season goes on, the later season monarchs carry a heavier load and do worse and worse.

Check out Dr. Altizer's web pages and you can test any further monarchs you have. If you have your cages and have not cleaned them out yet, you may still be able to test them as well using a wet q-tip.

Good luck,
Elisabeth

Here is a link that might be useful: Dr. Altizer's lab