What In The Milkweed?!

Milkweed Patch Mysteries and Insect Identification

I’ve discovered some weird and wondrous things searching for monarchs in our milkweed patch, but I’ve never come across anything resembling this U.M.O in our Minnesota garden.

Mystery in the Milkweed Patch. Have you seen these before?
Clay Pots for Smurfs?

These twin globes are securely attached to the bottom of this common milkweed leaf and look/feel like an accidental splattering of dried mud. However, their identical shapes and suction cup appendages suggest otherwise.

What lurks beneath the common milkweed? You tell me...
Here’s lookin’ at you

I honestly have no idea what these little brown globes could be, so I’ve assembled a short list. It needs a little work:

  • mini-wasp nests
  • clay pots for smurfs
  • googly eyes
  • insect eggs
  • insect chrysalides
Update: Thanks to everyone in the community who shared their experience to help me identify the foreign object on my milkweed. The mystery has been solved…

Many of you guessed that it was some sort of mud dauber or potter wasp. This is bad news for monarchs since the larva inside these domes feed on monarch caterpillars conveniently brought back to them by parents scouring milkweed leaves for monarch caterpillars.

Potter wasps are beneficial pollinators, but they're also monarch predators, taking monarch caterpillars from milkweed leaves and feeding them to their little wasp larvae. One of the many predators that keeps the monarch survival rate outdoors to under 5%.
On The Hunt | Photo by Barbara Eckstein

To verify their identity, I opened up the globes:

potter wasp larvae feed on monarch caterpillars
Out of Pot

While potter wasps are monarch predators, they are also beneficial pollinators in your butterfly garden. I welcome them as garden guests, but they’ll need to find a home outside of our milkweed patch!

Milkweed Mystery Bug 2

This odd looking fly was resting on the branches of our tweedia milkweed last spring:

This parasitic bot fly uses mice as its unwilling host to grow offspring. Discover the helpful tool I used to ID this mystery garden guest in less than 5 minutes!
Mystery Guest in the Milkweed Patch

This time I turned to a new resource for assistance:

Insect Identification Facebook Group

In a matter of minutes, I learned this was just a rodent bot fly (Cuterebra fontinella) passing through…

What strange foreign eggs, objects, or insects have you found on your milkweed plants? Leave a comment below:

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  1. I have tall healthy milkweed plants in one area. The flowers have bloomed. I’m fjndjng little holes throughout the leaves and a horrid wasp in top of every flower and going to the leaves. I never saw a monarch here this year. Last year I raised and released 20 from my habitat. I fear that this wasp like one I’ve never seen before is eating monarch eggs. I just never saw the monarch. What do you think? I tried blasting it with water. Did no good. I’m so disappointed.

  2. What can I do about the parasitic flies? They are decimating my caterpillars and chrysalis

      1. You can hang fly traps. They greatly reduce the amount of flies that attack the Monarch catipiller in its early enstar. They can be very smelly but highly effective.

  3. Do you have photos of wasps that visit Milkweed. I’ve seen one on my potted plants that seems to be looking for aphids. I don’t have cats on my plants right now so I’m hoping it’s an aphid preditor (sp)

  4. Hi Tony, I’m back with another question! I recently had 2 3rd instar, 1 4th instar & a 2nd instar in a caterpillar condo. I must have accidentally obtained tainted milkweed as my cats began to vomit bright green & wander aimlessly unable to eat. I rinsed them all off under water & softly patted w/a paper towel to try to remove as much pesticides as possible repeatedly & immediately offered them fresh, untainted milkweed…unfortunately I had to euthanize all 3 of the larger instars–horrible & heartbreaking. The smallest guy did make it & has been eating ok. This morning he/she molted & now this cat’s coloring is VERY worrisome(I will post pics on FB)…almost no white bands, dingy looking, what I believe OE cats look like. My question is, have you ever managed to save a cat that ate tainted milkweed & if so, did it have any issues as far as coloring/development? I have isolated this one as a precaution but the idea of having to euth another one of these guys is killing me! It has been a tough rearing season thus far ?

    1. Hi Jennifer, sorry to hear your cats were exposed to pesticides. We have been lucky up north. We have an abundant milkweed supply and our neighbors don’t use pesticides so we haven’t dealt with these issues. I have talked to others that have though and i know rinsing caterpillars has worked for a few. Unfortunately, if they’ve already ingested too much, there’s nothing you can do. OE doesn’t have ‘visible’ symptoms with caterpillars…just the chrysalides and butterflies. I hope things turn around soon…hang in there!

  5. Earlier in May I was able to successfully raise and release Gulf Fritillaries and green tree frogs in S FL. However, after the mosquito spray trucks began coming through, I have observed the demise of these creatures. Upset, I took photos of caterpillars which essentially died while turning into chrysalis, chrysalis which did not emerge, and dead baby tree frogs. My property is chemical-free and on a dead end street. Bats and dragon flies are no longer seen either. I am highly suspicious of the spray ingredients the county chooses even though officials tell us the chemicals are harmless and necessary to kill mosquito populations. Has anyone fought city hall or spoken up with success? How can we help each other with this problem? Others say if we complain and show proof, we become targets by government entities.

    1. Hi Nancy, this is a huge issue this season with the increased spraying due to Zika virus concerns. Yes, the spray is killing a lot more than mosquitoes. I’m not sure what the answer is…

  6. Hi. I’m finding a lot of what looks like misshapen monarch eggs. Not oval, more rounded, and a very pale yellow tinge coloring. Might they be unfertalized eggs? Placement on the leaf is similar to known egg location.
    Also, are aphids harmful to the caterpillar or egg? I raise mine indoors but worry about any aphids on the leaf. If these small things are not monarch eggs -should I get them away from my good eggs?
    Thanks so much.

    1. Hi Jenn, here are photos of monarch eggs. If they don’t look like this, it’s probably another insect egg:

      Monarch Eggs

      Milkweed should be rinsed when bringing indoors to remove aphids, disease spores, and potential predators. If there are a lot of aphids on the leaf, cut off a small leaf piece with the egg attached and place it on a new leaf…good luck!

    2. No aphids are not harmful to the Monarch eggs. However if they are not kept in check they can weaken the Milkweed, and eventually destroy it.

  7. I have been raising caterpillars for years now. My faves are the Monarchs. I love everything about them! This year, however, has been the most awful year for all caterpillars. I have only found two, one Tiger, and one Eatern Black. I have hatched three Zebra caterpillars from eggs, two died while very young, the third made it to half an inch in length, then suddenly died as well. I read that the mothers when laying eggs can transfer bacteria, or harmful pests that kill the caterpillars. My Eastern Black made it to his last I star, he attached himself to a branch, and then I found him dead as well. I have NEVER had this kind of problem in all the years I’ve been raising them. I cried over every death. Right now I have a brand new Zebra, I am being extra careful, and praying things turn out. But like I said, I’ve never seen so few caterpillars and butterflies since I’ve been doing this. I’m bewildered. The worst part about all of this is I have not found a single Monarch egg or caterpillar. I have seen only a couple Monarchs on the milkweed, and none have laid eggs. I’m so upset by this. I have noticed that there are a LOT of these weird red and black beetle like I sects all over the milkweed. And the aphids are out of control. Last year alone I raised and released 21 of them. I even tagged them! It was fun and exciting…this year is so sad. I’ve decided to take all of my gear and rewash it really well, and get some new stuff as well, I’m hoping that will help. But I was wondering, do you know if there is less butterflies this year? Would love some help in this matter. BTW, I live out in the country, on the Eastern Shore. Thanks so much, your website is an inspiration!! Next year I am building my own butterfly house and garden…I’m sure I’ll turn to you for advice again soon. Thanks!

    1. Hi Elisabeth, so sorry to hear you are having problems this season. Do you live in a region where there is increased spraying over zika virus concerns? Also, the monarchs had a freak winter storm hit the wintering grounds in Mexico this past March, while most were still there. Some survived, but the eastern population seems way down this season, based on reports across the eastern half of the country. Good luck with your new house and butterfly garden!

  8. I live in Central Florida and have many lizards that are running all over my butterfly garden. There are several different colors – brown, black, green and a light tan. I saw in your list of Monarch Killers that lizards are included. Is there any way to get the lizards to stay away from butterfly garden?

    I am going to use the mixture #1 for ants. Besides being on the ground they are also on the passion and pipe vines. Is there anyway to get the ants off the vines.
    Thanks for any information you can pass on.

    1. Hi Judy, sorry about all the predators crawling around your garden..I know they can be very frustrating! For the ants, I think you just have to give it a little time to spread throughout the colony. You could try hosing down the vines, but that would also remove eggs/caterpillars. good luck!

  9. Hi Helen,

    they need some time to adjust to being back outside. I actually cut back all the stems of our tropical milkweed and let them start putting out new foliage. I use the stem cuttings to start new plants.

    Your other option is to put them outside in shadier conditions and gradually move them into sun over the next few weeks.

    If these are mature plants, just pinch off the affected leaves and let new growth emerge. Good luck, Tony

  10. Hi Tony

    I started taking my milkweed out for some sun and air
    But noticed that the leaves are bleaching out or fading from a nice glossy green to a dull almost bleached light green did I kill them?
    They aren’t growing like before. I wish that I could send you a picture.

    1. Hi Mary, I wasn’t able to move them, but maybe I didn’t try hard enough. I’ve gotten a few good leads now so I will investigate tomorrow and report back. Thanks for your post!

      1. Potter wasp, yes. Predator of moth caterpillars, yes. Predator of monarchs, not likely. It is actually benefcial because it catches caterpillars of many moths, some of them may be pests.
        It is not a dauber wasp. Those make different types of clay nests, not cute liitle pots.
        The image is not that of a potter wasp but a vespid in a different subfamily, probably Polistes. You may want to replace that image.

        1. Thanks so much Beatrice, that one slipped past me! I fixed the photo…

          I don’t think potter wasps are common monarch predators like paper wasps, but I talked to someone else who found potter wasp nests on their milkweed too.

          It’s hard to believe they would build nests on milkweed if they weren’t feeding tussocks and monarchs to their caterpillar-fed larvae.

          Many species have evolved to withstand the toxins in milkweed…

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