I would remove the cats from the container and the food. Place them in a new container and add fresh food. Watch them and see what happens. If others die, then definitely throw out the lot. But, you may have had some other factor in the deaths of the caterpillars. You can't attribute all deaths to OE. Do the caterpillars look dirty? Sherry has mentioned that the cats have dark specks on them--not just darkened stripes.

Hope this helps,

Sandy

I tried comparing the stripes on the dead ones, and the others in that container, with cats from separate containers, but they all seem to have about the same amount of clarity of stripes/dirtiness. I had already switched containers and replaced the food--I do that twice daily anyway. I only hope my whole brood isn't sick. Time will tell. Thanks for the quick response.

Martha

Sorry that you are having to deal with sick & dying monarch cats. It has happened to me, too. I only raise a few cats each summer, typically 5 or 10. Each one is kept in its own small jar, open at the top, with the leaf in a very small cap of water. When they reach 3rd or 4th instar, I transfer the cat to a one quart glass canning jar, with a screen top, held on with rubber bands. But I follow the same rule, one cat per jar. I also wash off the milkweed leaves under a strong stream of cold running water, and dry the leaf, before feeding it to the caterpillar. And of course there is much hand washing and jar washing that goes on, as well. These methods enable 80 or 90 per cent of the monarch cats to emerge as healthy adult butterflys.

The Dreaded OE Spore

The Dreaded Tachinid Fly
I just read that they can also lay on eggs and first to second instar larvae, but most 3-4 instar larvae get parasitized. I think fall is most worst time for Tachinid predation.

Project Monarch Health Click on "Monarch Parasites" on this website.

I had Monarch adults checked once and not all the Monarchs that were reared together had OE. There is a possibility that some have an immunity to it.

Well, two more deaths, so I'll sacrifice the rest from that container. The rest that I have are all doing great and I keep finding more outside. I'm definitely going to keep everyone in their separate groups and keep any new cats in individual containers. Thanks for all the links and suggestions.

Martha

Have you checked out the FAQ section at the beginning of the forum?
Click here for FAQ website

Click here: Important Info RE OE & Monarchs!

There's more good information on caterpillar rearing and disease prevention in the FAQ section.

There are lot's of diseases that can affect butterflies. OE is just one. Also, environmental stresses can kill caterpillars. For example, if you bring them in to an air-conditioned house from the hot outdoors, a temperature drop of more than 10 degrees can do them in, or weaken them. If you handle dirt and then handle food material you may transfer bacteria to the food. As others have mentioned tachnid flies and parasitoid wasps can take their toll. One study saw over 20% of monarchs were infected with tachnid flies. So, that is why many of us collect eggs and raise the cats on well rinsed leaves. Or at least we try :)!

It sounds like you are handling it well though. Use basic sanitation methods between broods. Bleach water to clean cages and well rinsed after.

Good luck,
Elisabeth

Well, after reading this post I have started to realize that I may be taking on too much.

I had about 30 Monarch cats in different stages in three terrariums. This has always worked for me in the last few years. I place them in separate age groups so the young ones are in one tank, teenagers in another, and adults in the third.

Yesterday morning I found two cats in the gardens which were dead. I had made the decision that I would not bring in anymore until some had eclosed, but after seeing the this outside, I decided to go and get two more terrariums and brought in another 12+ yesterday.

This morning I find that one caterpillar tried to get into the crysalis form and only managed to get halfway done. It's just hanging there and there are three others in J form around it making it impossible for me to remove the sick one.

I work full time all day and the terrariums are great for morning and evening clean-up and feeding. Wouldn't be able to do it if each had their own container so, as I said, I may have to rethink...

Tiffy,

It sounds to me more like your caterpillars are suffering from a bacterial or viral infection, not Oe. What is the temperature like in your area right now? Has there been a sudden or unusually high increase in temperature (climate change)? This often causes this type of problem with Monarchs, or so I have found. What happens is that more of the various bacteria found in the soils will grow (makes sense, doesn't it? warmer temps, better conditions for stuff like bacteria and/or fungi to replicate? or at least for some?) and then, you end up with a variety of problems with your lepidoptera.

It seems to me that, Monarchs, in particular, are more susceptible to climate changes and what happens to the plants that they are eating. My own hypothesis is that the plants have a greater propensity to become inundated with the little microscopic beasties (fungi, bacteria, virus, etc.) that have a detrimental effect on the growth of the larvae. I have seen this time and time again as the weather changes. When the temperatures are cooler and more stable, the larvae seem to thrive. When the temperatures increase to ridiculous highs all of a sudden or for inordinate amounts of time (when normally it is milder), I have more larval deaths similar to what you are speaking of.

Don't be discouraged. Instead, continue taking precautions with removing those that are ill and sanitizing your containers, removing all leaves and providing fresh, DRY leaves. Try to be sure that moisture is kept to a minimum and air-flow is abundant.

As an aside: one of my former Kindergartners who is going into 2nd grade this year, found some Monarchs on the Milkweed she planted in her yard. Her mom texted me just last week while I was on vacation. Mom was very concerned about the health of a few of the larvae. Aliyah, on the other hand, was very matter-of-fact and was trying to explain that the caterpillars were sick and had to be removed from the healthy ones and euthanized. Mom wasn't so sure and wanted confirmation from me; hence the text as well as photos. Sure enough, this little girl was absolutely correct. She had 'talked' to the caterpillars (according to her mother), "I'm sorry little ones. I am taking care of you the best I can. I know you are sick." She blew them a kiss and then told mom what needed to be done.

So, hang in there. Keep in mind that less than 10% of the eggs laid by a mama butterfly actually make it to adulthood. When viewed statistically, you realize the disease issue is one that is astronomical.

I do cover some of this on my website.

CalSherry aka tdogmom :)

I highly recommend reading Tdogmom's info on Monarch diseases, both here on our FAQ and her website. She has studied this in depth and we rely heavily on her to provide us with diagnoses and treatment info as far as prevention and interception of these diseases. She knows what she's talking about for sure.

Susan

Thank you so much for the info... as always. Although I don't chime in very often, it's nice to know that those of us who wish to help can go someplace and get good responses in a timely manner and I do appreciate it. The three Js formed normally and don't seem to have a problem. Tonight I will try to remove the sick one. This is the first time in five years I've encountered such a problem.

The weather, as you said, may be playing a factor. About a week ago we had some abnormally high temps with humidity here in Nova Scotia. Things probably went haywire then. I am finding more dead cats outside than normal, but then again it's been a baby boomer year here for Monarchs. I've never seen so many. I could bring in another twenty or so - at last count there was 52 in the house - but will hold off for now and when this lovely bunch takes flight I'll start rearing the Mexico generation in early September. :O)

Again, many thanks for the help!!

I'm curious. Has anyone tried to use a microscope to see if there are any OE spores on an egg? The deal is that the caterpillar gets the OE from the mother and she deposits them on the egg when she lays it. The caterpillar eats the spores and becomes infected when it eats its egg shell, which they always do.