Milkweed Shortage Sparks “Alternative Fuels” for Hungry Monarch Caterpillars

Monarch butterflies have made their way to Texas, but unfortunately not much milkweed greets them upon arrival.  A harsh, dry winter preceded by drought and schizophrenic weather have left the sought-after perennial a no-show in many Texas gardens–and on roadsides and ranch land.

Milkweeds, that is, any Asclepias species, are the host plants to Monarch butterflies and the only plant on which they will lay eggs to continue their life cycle.

PUmpkin fed Monarch

The Monarch butterfly on the left was fed with pumpkin during its final instar. Photo by Ellen Reid

Reliable DPLEX correspondent Harlen Aschen wrote to the listserv that reaches hundreds of butterfly fans that on a 1000-mile trip from Port Lavaca, Texas, past San Antonio to near Abilene and back around Austin “we saw no blooming milkweed.”

Not good.

Yet that hasn’t stopped a tenacious group of butterfly lovers from raising caterpillars and hatching butterflies on “alternative fuels.”

Professional butterfly breeders have been experimenting for years to keep their livestock well nourished when host plants become scarce.    Many of us who raise butterflies at home, especially in a year like this, also seek alternatives, since local nurseries seem to be having a hard time getting milkweed and keeping it in stock.   The recent news that the Monarch butterfly migration may soon become extinct because of a loss of milkweed habitat is driving the demand.

So what’s a hungry caterpillar to do?

Hungry caterpillars on milkweed seedlings

My boys are hungry! Six Monarch caterpillars have pretty much decimated this pot of milkweed seedlings planted in February. Good thing I have another one. Photo by Monika Maeckle

It’s a quandary.   At my house, I planted Tropical milkweed seeds in February and have several pots growing, including two filled with seedlings only two inches tall.  This will sate my caterpillars for a few days, at most.

I’m hoping that by the time the hungry cats finish up the tender seedlings, my garden milkweeds will have taken off.  Or perhaps local nurseries will get more milkweed in stock.

Over on the DPLEX list, butterfly buffs–and the Monarch caterpillars–are getting resourceful.  Several folks mentioned that by the time the caterpillars get to their fifth instar, or their final stage, before morphing into a chrysalis, they will eat pumpkin and cucumbers.

That’s right, folks.   See it with your own eyes.

Monarch caterpillars eating pumpkin

No milkweed? No problem. In the fifth instar, Monarch caterpillars will eat a variety of pumpkins. Photo courtesy Ellen Reid

“The butterfly on the left was fed with pumpkin during its final instar.  The one on the right was reared on milkweed,” Ellen Reid wrote via email all the way from St. Arnaud, Victoria, Australia.  “We couldn’t distinguish between them in any way.”

Reid shared a photo of “pumpkin frass”–orange colored butterfly poop which is produced in volumes in the final stages of the caterpillars metamorphosis.   Usually the frass is dark green or even brown, but “pumpkin frass” looks like the food that fueled it.

Paul Addington tried feeding his Monarch caterpillars cucumbers.  It worked.

Monarchs eating cucumbers

Monarch caterpillars in the fifth instar will eat cucumbers. But they have to be FRESH cucumbers! Photo courtesy Paul Addington

“These cats are eating the skin of the cucumber,” relayed Addington. “These were organic, but still felt like they were waxy, so [they were] heavily scrubbed first.”

Addington said the caterpillars indeed preferred milkweed when given a choice.  “All 52 of mine finished on cucumber, looked great and joined the wild,” he said, adding     “UPDATE: must be fresh, crunchy cucumbers.…two-weeks-in-the-fridge cukes were rejected with enthusiasm….what an uproar!”

Pumpkin frass

The frass, or butterfly poop, of pumpkin fed Monarch caterpillars reflects the food’s orange tint. Photo courtesy Ellen Reid

Dr. Chip Taylor, founder of Monarch Watch, chimed in to the conversation, letting folks know that the alternatives have been known for a while.   “These alternatives have been utilized by many people in the past. They only seem to work for fifth instar larvae that are less than four days from pupating. Many of the larvae will not make these transitions successfully.”

So Monarch butterfly caterpillars appear to be more adaptable than we thought.

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31 thoughts on “Milkweed Shortage Sparks “Alternative Fuels” for Hungry Monarch Caterpillars

  1. Silk moth caterpillars are fed a “cake” made of mulberry leaves and some other ingredients. I wonder if milkweed leaves could be adapted to this recipie, and whether the resulting “cakes” could be stored. If so, we might be able to feed the cake to hatchlings that appear before their food source is ready?

  2. Recipie for silkmoths:

    Gather mulberry leaves. Wash the leaves in cold water and remove any bugs, etc. Chop the leaves into fine bits. Allow to dry. Grind dry bits into a powder.

    Dry powder can be stored.

    When ready to feed, Mix powder with some water. Shape into little cakes.

  3. I would be interested to know if the adults from 5th instar larvae fed on pumpkins and/or cucumbers have as many poisonous cardiac glycosides that deter predation as those who feed exclusively on milkweeds.

  4. If you are looking for native milkweed to feed hungary caterpillars and live near Wimberley, I have discovered milkweed where none was last year. I believe it was the 15 inches of rain and subsequent flooding that resulted in this treasure.

  5. I first learned about feeding pumpkin from Jacqui Knight of Monarch Butterfly New Zealand Trust.
    http://www.monarch.org.nz/monarch/
    You can do a search on pumpkin on their website in the far upper right of the above webpage.
    Several years ago when Jacqui told us about this. I did some searching and did find some references:
    http://nzetc.victoria.ac.nz/tm/scholarly/tei-Bio12Tuat03-t1-body-d5.html
    “Food of Monarch Butterfly (Danaus plexippus [L.]) Larvae in New Zealand” by G. W. Ramsay

    The most important thing to remember is that pumpkin and other alternative foods should only be fed to 5th instar Monarch caterpillars. If you feed earlier instars (larvae/caterpillars) they will not survive.

  6. I think I have solved my problem as to what was stripping my milkweed. I never found any cats so I know it was not them. I have many rabbits, I think they did it. Hope they are OK. Will put red pepper around next time.

  7. I may be soon running out of milkweed. I read that cucumbers treated with Bt would be toxic to caterpillars. I called our local co-op and asked about Bt, and they said that organic certification rules allow for some limited use of Bt, but that it would be applied on the exterior of the plant and fruit.

    Does this mean any organic cucumber that has been thoroughly scrubbed would be safe for the cats?

    • As far as I know Bt is not systemic; therefore, it would not be taken into the plant tissue. You could peel the cucumber. That is what I did to my pumpkin. Then, cut it into cubes, put a hole through the middle, and then put it onto the milkweed stems. It worked.

      • THANKYOU soo, much my caterpillars r on the pumpkin,…, they have stripped all the swan plant leaves,….yesterday there were leaves, now none, the pumpkin peices r doing the trick.
        Thanks.

  8. It seems every website indicates that the monarch caterpillar will only eat milkweed. Well, my monarchs are a bit more adventuresome. Apparently monarch eggs were laid on my parsley, dill, cilantro, and carrot plants because caterpillars are feeding on each of these plants (there are more caterpillars on the parsley than the other plants). And no, these are not swallowtail caterpillars. I also have a number of them on the parsley and dill plants. So, if the monarch caterpillars only feed on milkweed, why are they doing very well on the parsley and other plants in my garden (I have only one milkweed plant and that has not been used by the monarchs)? Any ideas? Thanks.

  9. Thank you so much for this post. I wish I had found it before I had to make emergency runs to the railroad tracks and prairie to feed our 44- 5th instars. There are organic cucumbers in my garden I could have used. Also I may have been saved from my first severe case of OE. We’ll do this the next time we have several 5th stars at once. Thanks again !

  10. I found this site while looking for information on Monarch caterpillars eating other plants. I live in Minnesota and grow hundreds of milkweed plants of different kinds all through my 1/3 acre yard. Today I found a Monarch caterpillar eating a mustard leaf and starting to prepare the silk in said leaf. I went back and forth between the laptop and the caterpillar and unless the eastern black swallowtail has develop the sets of alternating yellow, white, black, white and yellow strips what I have there is a Monarch. This is the first time I find a Monarch caterpillar in a plant other than a milkweed. I do believe the are starting to adapt even when they don’t have to. A big plus is that this year I have more Monarch caterpillars in my yard than ever before. Nice site.

    • Hi Carmen
      I’m betting your caterpillar is not “eating” the mustard leaf, rather, it’s spinning the silk button to form its chrysalis. Monarchs and other caterpillars often leave the host plant to form their chrysalises. Keep an eye on it and let us know what happens. Good luck! – MM

  11. Thank you so much for the tips! I live in California near Pismo Beach and was so sad to find Monarch caterpillars on milkweed that was completely eaten up. I took the two largest home. One made a chrysalis last night and the other is happily munching on an organic persian cucumber. 🙂

    • Is there a specific type of squash or cucumber that seem to be more appealing to the cats? I just tried cucumber and they are at least giving it a try, but not devouring it like milkweed.

      • Mine eat the thin skinned Persian cucumbers. I even have a tiny 1st – 2nd instar that has been feeding on it. The just eat the skin, btw

  12. 7/31/2019 I just found two monarch caterpillars eating my dill! So excited as we don’t have much milkweed around here anymore. I have pumpkins and cucumbers in my garden; I’ll try that to see if they’ll eat it! 🙂 🙂 This is from southwestern PA.

  13. I got my catapillars eating organic cucumbers. They wouldn’t touch the cheap 99 cent ones. Guess they know what’s good.

  14. I feed my Cats on; Milkweed Vine
    (Cynanchum laeve), it is abundant regardless of weather. Monarch females will often lay eggs on them naturally as well. Easy to cultivate and grows just about anywhere, although it is considered a noxious weed in many states. It may well be what the wild population needs to survive for a while.

  15. Help! My large caterpillars all seem to be leaving their plants, crawling through mulch and whatever else to go I don’t know where. Is this normal? There are still plenty of leaves on the milkweeds, many multi-leaved stems, there doesn’t seem to be any competition for food.

    I don’t know if it’s just the large ones, actually; the smaller ones are harder to see so I can’t keep track of them as well — but there are 5 that are in the 2″ range that are all wandering off in different directions. They move fast too — they just pick a direction and start going very determinedly. Are they lost? Should I pick them up and bring them back to the milkweed? Should I leave pumpkin and cucumber about the yard, per some of the comments above?

      • Thank you! Sorry, I’m totally new at this and don’t really know what to expect. I just planted milkweed two months ago and am fascinated following this process. I’ve now found two them hanging upside down on other plants ready to make a chrysalis so I think you’re right, that’s exactly what’s going on – thank you, and sorry for the panic!!! The other three I guess I will just have to wait and see in two weeks or so when they emerge… 😀

  16. Last year I planted dill, got quite tall. One morn went out and it was covered with monarch caterpillars. Within 2 days it was gone.

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