Disease?

[temperance]

This is the second year my wife and I have reared and tagged monarchs.
Last year, we noticed that some of the cats at the "hanging" stage -- right before they turn into a crysalis -- became discolored. They didn't have that J curve and just lingered at the top of the jar (we used mason jars with a mesh top). Some were hanging from a string, attached to the top and looking like they were intending to get to the next stage, but they were hanging further away from the top than normal. After a day or two there would be white, stringy discharge hanging from cat and it looked sort of skinny and eviserated. Needless to say, they didn't make it to the next stage.

Any ideas?

Am I deling with Ophryocystis elektroscirrha?
http://www.monarchwatch.org/biology/control.htm

We're using the mesh tent this year and have one that looks bad. I'm worried about it possibly infecting the others.

any insights would be much appreciated. Thanks!

[Jim]

Does this look similar to the "white, stringy discharge" you observed:



If so, then your caterpillars were parasitised by a Tachinid fly. The female flies seek out and oviposit on the larvae. The tiny brown casings that you may also observe are fly puparia. The flies are smaller than house flies and are gray in color. The female flies are quite persistent and are difficult to keep out of cages made from netting. They may also have the ability to lay eggs on larvae through the netting e.g., when the larvae are crawling on the netting rather than the plants. Fortunately, unlike most Lepidoptera, the monarch has relatively few fly and wasp parasites to contend with. One reference indicates that 5 tachinid species have been reared from monarch larvae and pupae. In some locations the flies kill more than 90% of the larvae not found and harvested by spiders, wasps, earwigs, lady bugs (beetles), lacewings, ants, stink bugs and other predators.

You can read more about this parasitoid (and view more photos) in the July-November 2003 Updates at

http://www.monarchwatch.org/update/

The best way to protect developing larvae from predators and parasites outdoors is to find them early in development and enclose the plant they are feeding on with a tightly sealed mesh bag - we offer Insect Rearing Sleeves for just this purpose (or you can make your own):

http://shop.monarchwatch.org/product.aspx?p=113205

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[temperance]

That's exactly what it looked like, including the discoloration. We lost about 10 last year because of it.

Thanks for the tips. I'll pursue the prevention methods you suggested.

[monarchrose]

Hi Jim,

I had one caterpillar have the pupation problem described in an earlier post. And this past week I had 5 chrysalides die. They had turned black and I assumed that the butterflies would emerge the next day. Well, I was watching one and a maggot came out instead, hanging from a white thread. Later that day I found the others with the white threads. yuck. I assumed this was a Tacinid fly problem. I raise most of my cats from eggs, but these were gathered after our vacation and some were first instars. The other possibility was that a fly got into my net tent. It could have followed me through the door. I have raised about 60 - 70 caterpillars this past month, so I suppose I should be happy about the ones who have made it.