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Unlucky Butterflies

The Unintended Consequences of Human Intervention
Jeannine
Sep 14, 2022
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Please Note: This video depicts about twelve and a half minutes, accelerated four times (from August 26, 2022, beginning at approximately 8:15 AM).

Acting Against My Nature

I am a vegetarian and a lifelong lover of all animals, including insects. I have many happy childhood memories of bringing wild caterpillars into the house in order to witness their metamorphosis into butterflies. The best part was releasing them back into the environment after the change. My favorite butterfly species has always been the Monarch.

I was recently forced to euthanize a Monarch butterfly, the very one featured in the video clip above. I still feel horrible. So why did I commit this heinous deed? Please allow me to explain.

The Plight of the Monarch

The Monarch butterfly has recently been classified as endangered by the International Union for Conservation of Nature. According to the World Wildlife Fund, the main cause for this catastrophe is the lack of milkweed plants. Monarch butterfly caterpillars only eat milkweed, but herbicide use, habitat loss, and unusual weather conditions have greatly reduced this crucial food source. But a reduction in host plants is only one of the problems that are pushing the iconic butterflies towards extinction.

Apparently, Monarchs have become more susceptible to infection by parasites and other pathogens. I’ve noticed more diseased caterpillars in my yard this year than in previous years. According to the National Science Foundation, "One contributor to the rise in the parasitism rate is the increased density of monarchs in places where they lay their eggs... the increased density may be due to many factors, including the loss of wildlife habitat; the widespread planting of exotic, nonnative species of milkweed; and by people raising monarchs in large numbers in confined spaces." (NSF, Monarch Butterflies Increasingly Plagued by Parasites, para 9).

Some groups have been raising and releasing large numbers of Monarch butterflies, hoping to help the species to survive. Less altruistic companies raise and sell butterflies intended for release at weddings or funerals (this may be a beautiful, symbolic display, but the released butterflies might not be able to find appropriate food sources or egg laying sites if they've been shipped to a location outside their native range or in the wrong season). It is possible that captive bred butterflies may lack the genetic diversity and robust immune systems of their wild brethen and infected individuals could also spread parasites to the wild population. Many experts believe that the seemingly innocent practice of rearing Monarch caterpillars might actually be contributing to the demise of the species.

A Still image from the video, about ten minutes post eclosure - note the stunted, winkled wings.

Infected Butterflies

Earlier this summer, two Monarch caterpillars climbed up a window on our house, where they decided to pupate. Soon they transformed into two beautiful little jade-green chrysalises. Monarchs eclose (i.e., emerge as a butterfly from the chrysalis) in ten to fourteen days, so I marked my calendar and happily awaited the appearance of beautiful butterflies. As the time for the first eclosure drew near, my excitement began to infect the whole family; my husband even made plans to film the event. Finally, the chrysalis’s shell began to become transparent, a sign of the imminent emergence of the butterfly, and my husband rushed to set up his camera. It was wonderful watching the beautiful new Monarch emerge from and cling to the remains of its chrysalis. It seemed that all was going well until, after approximately twelve minutes, the butterfly abruptly fell. What happened?

After some research, I realized that this butterfly had been doomed to failure long before pupation. Stunted wings and physical weakness are signs of Ophryocystis elektrosirrha infection (aka OE), a protozoan that infects Monarch and Queen butterflies. If you compare the video still of the infected butterfly above (about ten minutes after emerging from its chrysalis) with the photo of the healthy butterfly below (approximately five minutes post eclosure), it is plain that something had gone very wrong with this unfortunate individual.

The healthy Monarch butterfly that was featured in my Return of the Monarch article.

I finally found the infected butterfly several hours later and rescued it from some ants. It seemed healthy, except for the fact that its wings were a shriveled, useless mess. I tried to put it on a flower in the garden, but it was not strong enough to hang on and promptly fell off. It was clear that it would never fly: "Newly emerged butterflies must be able to hang down so their wings can expand and dry properly. If they don’t have room to do this, wrinkled and deformed wings will keep them grounded for life." (Tony Gomez, Butterfly Birth…, para, 13). Mr. Gomez suggests three options for a healthy, but grounded, butterfly: “It can be kept as a pet, left outside to support the ecosystem, or euthanized." (Tony Gomez, Butterfly Birth…, para, 14). Of these three choices, keeping it as a pet seemed the least cruel, so I put it into a mesh enclosure for a couple of days, feeding it on cut flowers from my garden and hummingbird nectar. Unfortunately it continued to weaken until it could no longer eat. At that point, I realized that euthanasia was kindest path.

Something Very Bad Is Happening to the Monarchs

A possible victim of Black Death, aka as Nuclear Polyhedrosis Virus (NPV)

I have noticed other indications that this year’s local Monarch population may be facing more issues with pathogens than usual.

In mid-August, I found a very dead caterpillar in my garden: It was shriveled and blackened, but still recognizable as a Monarch larva. I suspect this one was killed by a microbial infection, possibly Black Death, aka Nuclear Polyhedrosis Virus (NPV), a nightmarish virus that kills caterpillars by entering "...the nucleus of infected cells and reproduces until the cell begins to produce crystals in the fluids of its host. The host becomes swollen with virus-containing fluid, turns black, and dies." (Jungle Dragon, para 1)

Tachinid fly pupae (from Death of a Monarch) - I didn’t have the heart to repost a photograph of their victim.

In July, I found another caterpillar attached to a weed I’d just pulled. It was just beginning to pupate, so I brought it into the house so my family could enjoy watching it become a chrysalis and eventually emerge from the chrysalis as a butterfly (see Death of a Monarch for the whole sad story). It turned out that the experiment was educational, but not in the way I'd hoped: The caterpillar had been infected by Tachinid fly larvae, so instead of transforming into a lovely jade-green chrysalis, the poor Monarch larva died and four Tachinid fly larvae rappelled down from its body on strings of white, mucus-like material. Tachinid flies are often released into gardens as an organic defense against crop destroying insects, but, unfortunately, they are an indiscriminate weapon: They infect and kill pests like cabbage loopers, tent caterpillars, and tomato hornworms, but they will also attack Monarchs and other harmless and beautiful butterflies.

So what the heck is happening? I never encountered any of these horrible diseases when rearing caterpillars into butterflies as a child.

O.E. infection rates among wild Monarchs is increasing. The U.S. National Science Foundation found that “…the O.E. infection rate increased from less than 1% of the eastern monarch population in 1968 to as much as 10% today (NSP, Monarch Butterflies Increasingly Plagued by Parasites, para. 2).

Pathogenic infections of wild Monarch butterfly populations - such as O.E., Black Death, and infection by parasitic insects - seem to be increasing. However, captive breeding is probably not the only reason this is happening. The use of insecticides and herbicides (both chemical and biological controls), along the loss of habitat, is responsible for much of the damage. According to Lupine Gardens, the limited supply of milkweed plants increases larval and pupal deaths by infection or predation:

“Let's say you have a small patch of milkweed. A female Monarch comes along to lay her roughly 250 eggs she needs to depart with. She comes upon your small patch and is forced to lay more eggs than is typically necessary in a wild area which is abundant with milkweed. Now you have an imbalance of caterpillars per plant. Now you have an imbalance of caterpillars per plant. As the caterpillars go through their instars and devour more and more plant material, the plant sends out a distress signal through pheromones. An SOS to stop the plant from being decimated to the point that it will be susceptible to disease and possibly killed off. These pheromones disperse through the air until parasitoids that are waiting nearby pick up the signal. They then move in to help the plant by parasitizing the caterpillars as need be. Again, the percentage is based on the excess of caterpillars on the plant. So initially, they may parasitize a few caterpillars and move on. If the plant is still in distress after a few caterpillars are eliminated, the plant will again repeat the process and more caterpillars will be eliminated. This process ensues until the plant is able to regenerate tissue as fast as the caterpillars can forage. A sensible balance.

“The takeaway from this is that your caterpillar losses will be greater in an area that does not have the potential to feed an abundance of caterpillars naturally. The importance of creating larger, more diverse habitats is crucial to the overall success of high percentage survival rates.” (Lupine Gardens, Importance of T-flies & the truth behind Monarch numbers, paras. 7 and 8)

The bottom line is that the Monarch butterfly is in trouble, and we humans have pushed them to the brink of extinction. We need to help, but how?

Stop the Extermination of Monarchs

  • If you decide to purchase commercially raised butterflies (eggs, larvae, pupae, or adults), be cautious. While some responsible facilities are working hard to ensure that their stock is free of infection, captive bred butterflies may still lack their wild counterparts’s resistance to disease. And if a facility does not take steps to avoid selling infected butterfly larvae, the adult butterflies may subsequently spread these infections to the local population.

  • Please do NOT host a mass release of butterflies to celebrate a wedding or other event - it’s visually pretty, but potentially cruel to the butterflies. Homing pigeons could be a kinder alternative, and also make for a pretty impressive display.

  • If you have the space, plant milkweed - but make sure it’s the right kind (i.e., native to your area). Better yet, if there is a wild stand of milkweed on your property, leave it alone for the Monarchs.

  • Plant flowers that adult Monarchs can use as nectar sources - even flower pots on your patio can help feed hungry butterflies!

  • Avoid the use of herbicides and pesticides.

  • There is no probably no reason for children to stop raising Monarch caterpillars (except in California, where it is now illegal) - it is a great learning experience! However, if one decides to rear a caterpillar for eventual release back into the environment as a butterfly, do it right: Use airy, CLEAN enclosures for the caterpillars’s temporary homes. If the container has been previously used to raise caterpillars, be sure to disinfect it well, to avoid infection of the new tenants. There are a number of web sites that offer advice on the proper raising of Monarch caterpillars (DeannaCat’s offers an excellent web page on the topic).

  • Educate yourself about Monarchs and spread the news of their plight - help save the Monarch butterfly!

The butterflies will thank you.

Photo by C. Formanski, as an employee of the US National Park Service., Public domain, via Wikimedia Commons

References

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