Could be the OE parasite, a viral or maybe even a bactierial infection. OE is an automatic death sentence, viral is very hard to completely clean out and bacterial, while easier to deal with is still not easy to completely eliminate. Best thing to do for the species would be to destroy them all.. the livestock both in your cages and still on the plants outside, and the plants they were on both in and out. Sterilize all your equipment and wait for another time to rear them again. It could be that OE is heavy in some of the places that have year-round plexippus colonies. In those colonies OE can be present in as high as 3/4's of the entire colony.
FWIW

Wow, so sorry to hear about the problems with your cats! I have never had that happen - knock on wood - on a larger scale. I have lost 1 or 2 over a rearing period, to be sure, some due to my own ineptness (is that a word?).

Is TM perennial in your location? Being North of you, I plant new seeds every year because it performs as an annual in my climate. I often wonder if more problems crop up in areas where A. curassavica is a perennial or reseeds. I know some diseases can persist in seeds as well, e.g., specifically, tomatos.

I am rearing about 11 Monarchs now and they are getting into 4th instars. So far, no deaths or indication of disease, but as Larry has said, it often goes unnoticed, without exhibiting external symptoms. Didn't you say that, Larry, in your other post? Correct me, please, if I am wrong. My TM is very clean right now. Unusual, but my normal population of aphids disappeared about a month ago after the Ladybugs showed up, rain, etc. I know this doesn't mean that OE isn't present on the foliage due to nectaring Monarchs and Monarchs that have layed OE-infected eggs, but I haven't had any Monarch eggs or larvae until now. So far, the larvae "appear" to be okay. OE spores are tough to get rid of.

I am so sorry, once again, but I agree with Larry, that if you even suspect OE, destroying the larvae would be in the best interest of the species and future generations.

I think there is a way to detect it with the use of a microscope. CalSherry, who used to post here (haven't seen her on here in awhile) described how to do this, and it doesn't have to be a very sophisticated microscope. But she also has a website, and I'm attaching a link on how to visibly detect OE in caterpillars from her website.

Susan

Here is a link that might be useful: Detecting OE in Monarch Larvae

Sorry to hear about your Monarch babies. :( It's too bad, especially since the species will have a hard enough time navigating your state with the drought conditions.

I too have some mortality every year, mostly due to my fumble fingers, or as Susan said - ineptness! But I lost some small instars due to too much moisture. Also had a couple random chrysalises that turned black and died for no apparent reason (i.e. when their siblings had perfect chrysalises).

This year I took some semi-random samples of the abdomens of the fresh butterflies, to look for OE. It is quite easy to do. Don't have a microscope yet, but either I'll get one, or my son will examine them for me at the lab in his school.

Thanks Larry & Susan!
I will destroy the cats I have in the house & will cut down all my milkweed! ;o(
I will need new seeds from some of you generous BF gardeners...Tropical isn't perennial for me either here west of DFW!
Large Milkweed Bugs (Oncopeltus fasciatus) are sucking the life out of the few seed pods I have!
It's a heartbreaking year here! I raised 13 monarchs earlier in late August/September & all were healthy! Now every cat is dying...I even saw a small white maggot looking thing come out of one of the cats so all will be destroyed & I will clean out all my boxes & sterilize my vases with bleach. I have been having at least 20-30 adults in my garden daily nectaring & mating & now getting infected possibly...so down with the milkweeds!!!
I read all your posts about OE Larry & know what I need to do now! No more monarchs for me this year!

Susan,

As always my thoughts are my opinions based on many years of actually doing, not just accepting what others say. So they are only FWIW to be taken as a person chooses to take them.

IMO common logic dictates that like with most infestation, disease or infection, the level they intrude an individual at can vary widely from minor to massive. That is commonly proved out with OE in Danaidae. If a larvae makes it through complete metamorphosis to an imago that can eclose and form OK, even if OE is present it was a relatively minor infestation in that individual. The opposite being if a larva at any instar, pupa or adult that has OE dies without getting through complete metamorphosis, that individual was obviously infested at a much higher level. Unfortuanately no matter at what level (with OE especially), failure to destroy any sick livestock whether it be OE, another parasatoid, viral or bacterial infection in most cases will promote the spread of any of any of them to other individuals. OE is the prominent one that will carry on to generation after generation beyond a given brood, and nothing but complete elimination of any brood within your control that might be infected with it will help slow it down in a colony. Why in my opinion when it comes to livestock even suspected of possibly having OE it's not worth taking any chances with them "for the good of the species as a whole". For those of use who did/do field work with Lepidoptera, that includes wild Danaidae livestock found or adults netted that show any possibilty of hosting OE.

NOTE: Even if you have a very strictly controlled gardening and rearing rigime (which I doubt any of you have), you won't eliminate all of any OE present. So don't go slap happy destroying everything in sight. Instead be analytical and logical, and then decide what is reasonable for your own circumstances.

Yes, livestock can have OE and not show any of the so called "visible" signs of it, which IMO are not proof positive of OE anyway and can be from other causes. In part why on my OE thread I offered some habit and condition factors that could also suggest OE is present as well even though they also do not prove OE and can also be from other causes. Bottom line, to prove OE is NOT present in an individual for certain takes a microscope or loupe. And in almost all cases if a larvae it will have to be euthanized to test with any certainty. A possibility to check for OE in pupa is to test the purge of the last instar larva for OE, but unforunately that is not 100%.

I'm a lot more scientific in my appraoch to Lepidoptera than all of the folks here, so I don't accept things at face value. I am also skeptical of data from other sources that are not proven to me. The Internet and publications commonly breed misinformation about everything, including Lepidoptera, that is passed on by ACE's who probably got it from another one. So it's prudent not to trust every thing you read on the Internet or in books if it's not from a source you trust.

Larry

I totally concur, Larry, about Internet sources and book sources being suspect. I think you have to have some degree of what sources to trust and not to trust. Sometimes I believe that one has an "instinct" towards valid research and sometimes that develops over time as one studies a subject and is exposed to the good and the bad and is able to filter out the bad. Simplistic, I realize.

Anyway, one of the sources on OE I have come to respect and believe, are the studies done by Dr. Sonia Altizer at the University of Georgia, who heads up the Altizer Lab at the Odum School of Ecology.

Lila, you can e-mail them and get an OE testing kit (free, as this is an on-going study). They give instructions on how to test the adult Monarch and samplings are sent back to the Lab for testing. Results are then sent back to the individual/group.

Research papers on OE are also available on the website. One particularly fascinating study was done by placing ONE spore on 2nd instar larvae that was then retested when the adult butterfly emerged, resulting in a finding of over 100,000 spores developed during the intervening time period! That's a pretty big statement on the virulence of OE, IMHO.

Anyway, thought you all might be interested in reading some of the research papers and perhaps requesting a kit to test for OE in your own backyard.

Susan

Here is a link that might be useful: Altizer Lab Monarch OE Project

Susan,
I have some advantages when it comes to sources over most of the folks here. They come from many years of association, colaboration or field work with a lot of Lepidopterists worldwide, access to their resulting research papers and their books. Those associations gave me a feel for the individual and their methods, good and bad, that when coupled with my own field and rearing experiences tells me whose work I do trust and whose I consider questionable at best. Another advantage is I often recognize whose work is being passed on (copied), also giving me a clue about new to me people. I can assure you that with a lot of books on Lepidoptera, the author did not do the field work for a large portion of the data given, if any. IOW, anybody can assemble a book or web site on Lepidoptera without having ever done any or very limited personal field work themselves. Over time some true to the science change, while some get much better some get much worse. Those who constantly seek to gain new knowledge via their continuing field work and research get better and usually remain true; those who start doing it for the almighty buck usually do not. Some super dedicated individuals I once held great esteem for I no longer do. But then you know how strongly I am against exploiting wildlife for financial gain no matter under what pretense except for a couple of specific reasons.

Lila,
"...don't go slap happy destroying everything in sight. Instead be analytical and logical, and then decide what is reasonable for your own circumstances."

That is the best advice I can give you IMO - I wasn't there to experience exactly what has traspired on your property, have no idea how sevier the infestation is or know what the state of it currently is (and you wouldn't either). But more than enough information is available about OE to study and draw your own conclusions from... "and then decide what is reasonable for your own circumstances." The key word is "reasonable".

Larry

Ineptness huh... LOL

IMO there is no valid excuse for handling livestock with club fingers or those long painted talons some ladies like to wear on their claws. Every imaginable tool has been designed and made available for handling leps and their livestock. And resonable facimilles of them can be made simply from common household items that are or nearly are as serviceable as those bought from biological supply houses. When in the wilds I always wore a small fanny pack on my side just to carry any tools, homemade ovum, larva and imago containers, a small pad for field notes, a GPS and anything else that might be needed with me no matter where I hiked to. Those tools I used almost endlessly where worn around my neck on leather lacing and either tucked in a shirt pocket or just down inside the shirt to be out of the way until needed. When my ex and son were with me on outings they also wore kits of their own to use. So it would be pretty simple to have a small kit for them when out in your home gardens, and a second kit indoors where you do your rearing. Just some food for thought that the Lep Devil made me bring up. ;)
Larry

Oh, Larry, I already feel bad enough about my "ineptness"......

I fear I am just getting too old, my fingers too shaky, jerky, whatever, they just don't go or do what I transmit from thought to brain to hands. Failure in synapse or neurotransmitters, or something. Tools would probably be even more dangerous in these hands of mine.

Good suggestion all in all, but I doubt I'll be doing this much longer, so the larvae will at least be safe from my quaking, quivering fingers (now I sound like the Wizard from Oz).

Susan

Would someone mind giving me the full name of this mysterious "OE" virus?? Planning on doing a little research later on this week to prevent this from happening here as well.

OE is shorthand for Ophryocystis elektroscirrha.