Monarch caterpillars not pupating

5 years ago

Eight days ago (October 15), a neighbor posted on Next Door that Monarch caterpillars had decimated her 15 milkweed plants to the point that there were no more leaves and they were eating the stems. I had Monarch caterpillars over the summer and my milkweed supply was pretty bare, but I at least had some so I offered to take the 4 cats she had remaining. For the next couple days, the cats were on my protected back porch eating on milkweed in containers. My limited milkweed supply was dwindling fast, plus, night temperatures were getting down to the 50's, so I moved the cats to an enclosure indoors that I put back on my covered porch during the day when the temps were warm enough. To stretch out the little bit of milkweed I had left, I supplemented with cantaloupe which I have used with Monarch caterpillars in the past and had good luck with. At all times, there was milkweed in the enclosure.... I just could only bring in a few leaves at a time and as they were close to being completely consumed, I brought in more. I made sure the milkweed was always fresh and not dried up. I observed the caterpillars eating both the milkweed and the cantaloupe. All four caterpillars seemed healthy and were getting fat. On October 19, two of the cats climbed to the top of the enclosure and soon after that, went into the J formation. The other two cats followed suit on October 21. Today is October 23 and none of the four caterpillars have pupated. They have straightened from the J and are just hanging there.... and they are all shrinking. They are still alive because I can see them twitch and make slight movements occasionally. It is like they are trying to form into a chrysalis, but can't. I am really concerned and at a loss about what to do. I don't want to be too hasty if they will indeed form a chrysalis, but I also don't want them to be miserable if they are doomed to not progress any further than this. Has anyone out there who has raised Monarch caterpillars ever experienced anything like this?

Not the best photo. The cat in the middle attached on Tuesday, four days ago, and is much thinner than the other two that attached two days ago. The fourth caterpillar is hanging on the other side of the enclosure.

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Comments (5)

four (9B near 9A)
5 years ago
>"doomed to not progress" ___ True.

>"don't want them to be miserable" ___ That is the right way to think. Freeze them.
sheltie6
Original Author
5 years ago
Thanks! I have never had to euthanize a caterpillar or butterfly before and wanted to make sure that was the right thing to do in this case. No doubt it was. I heard it is good to put them in the refrigerator first so that it isn't quite a shock when they go in the freezer, which is my plan. When I removed them from the enclosure, they seemed light and on the dry side, especially the first two that attached to the top of the enclosure. If anyone who has any idea what would have caused this, please let me know. I did some searching online and found information about Black Death and other possible reasons, but nothing I read seemed exactly like this situation. The cats I had were probably 3rd to 4th instars when I got them and had very little to no milkweed up to that point, so they had most likely gone through a period of malnutrition. Once I got them, there was a constant supply of milkweed and cantaloupe. I use NO chemicals in my yard, pesticides or herbicides. I had other caterpillars this summer that did just fine and also ate cantaloupe, although, not the same cantaloupe. I rinsed off the cantaloupe before cutting it and putting it in the enclosure, but now wonder if there could have been some trace pesticides on the cantaloupe??? So... my hunch is that either malnutrition/starvation during their development led to their demise, or there was something bad about the cantaloupe. Or, they could have come into contact with chemicals before I got them. All I know is that they seemed happy as can be and were steadily growing until they attached to the top of the enclosure, but after that, they were not able to form into a chrysalis. : (
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four (9B near 9A)
5 years ago
last modified: 5 years ago
OE spores transfer from adult onto eggs that it lays.

>"likely gone through a period of malnutrition" ___ Also a possible cause.

>"rinsed off the cantaloupe" ___ Our food integrates pesticide as it develops.

You could watch for Tachinid fly pupae descending from these caterpillars.
sheltie6
Original Author
5 years ago
Thanks again. I don't see any signs of Tachinid flies, but I do highly suspect OE.
PRO
Maid For You Cleaning
4 years ago
last modified: 4 years ago
so iI don’t want to act like iI know something but iI did research on OE. It seems that it is rare for it to kill itsit’s just, because it relies on the host to survive. Alternatively it appears the development on the adult butterfly and it’sits wings. i would look into ”black death”, if that is the case, i would read up on how to disenfrct the cage and prevent the spread😞 hope this helps! And thank you for being so kind and caring