Milkweed Butterflies Are More Lethal Than They Look


Butterflies look gentle as they fly from plant to plant. But some may be more lethal than you think. Naturalists have recently witnessed several species of milkweed butterflies harassing, subjugating, and then feeding on milkweed caterpillars, possibly to replenish toxic alkaloids inside the larvae.

This behavior is described in an article Published Wednesday in the journal Ecology. The paper’s authors say they are not aware of any similar behavior documented among other butterflies, or any insect so closely related for that matter. While butterflies have previously been observed feeding on locusts harboring toxic alkaloids, no one had documented adult butterflies stealing such compounds from their relatives.

Scientists didn’t have a word to describe this toxic behavior, so the study’s authors came up with one: kleptopharmacophagia.

The discovery was made in December 2019 when two friends traveled to the Tangkoko Batuangus Nature Reserve in the northern part of the Indonesian island of Sulawesi. Yi-Kai Tea, a graduate student studying ichthyology at the University of Sydney and the Australian Museum Research Institute, and Jonathan Wei Soong, a naturalist from Singapore, share a passion for macro photography and butterflies and have decided to spend their vacation photographing the sea. The reserve’s stunning array of fluttering insects.

Most of the butterflies the couple hoped to see were milkweed. There are about 300 species in the group, all of which are poisonous to predators, including the iconic Monarch. They gain most of their toxicity by feeding on alkaloid-rich plants and have a variety of bold and bright colors that serve as a warning to potential predators.

On the first day of their journey, the two men visited a wooded area on the beach and came across a butterfly bonanza. Hundreds of milkweed butterflies of several species were swarming around a vegetation near the forest floor, a rare sight even in this lush reserve.

Delighted, Mr. Tea and Mr. Soong spent hours photographing the insects. At the end of the day, the two men realized they were documenting strange and sinister behavior as they went over their pictures.

After making the first observation, Mr. Tea and Mr. Soong spent the next two days in the field doing their best to document the horrific drowning in more detail.

“We thought it was really cool,” said Mr. Soong, adding that he found the milkweed butterflies “a kind of metal.”

Mr. Soong and Mr. Tea spent hours watching seven different species of milkweed butterflies, including Blanchard’s ghost and the ismare tiger butterfly, both dead and alive, scratching so vigorously with strong claws on their feet that the caterpillars’ internal waters leaked out. . . They said the behavior cannot be described as predatory because many caterpillars have survived the encounters.

They also observed butterflies doing the same to the leaves of plants known to contain toxic alkaloids. As caterpillars, milkweed butterflies eat leaves loaded with pyrrolizidine alkaloids to make them unpleasant to their predators.

Having a stable source of pyrrolizidine alkaloids is also important for male milkweed butterflies. These alkaloids are a component in mating pheromones, as well as in marriage gifts, which are spheres of sperm and nutrients that males hold onto their partners’ bellies during sex. Of the dozens of butterflies that Mr. Tea and Mr. Soong saw scratching leaves and caterpillars, only one was female. This imbalance supports the researchers’ hypothesis that milkweed butterflies attack caterpillars to keep toxic alkaloids in the body of their prey. However, more research is needed to confirm this.

“One of the highly desirable follow-up experiments would be to see if the compounds actually transfer,” said David Lohman, co-author of the study and an insect biologist and associate professor at the City College of New York.

Mr. Tea believes this type of butterfly-caterpillar violence is not unusual. “Butterflies have a repertoire of really disgusting and bad manners,” said Mr. Tea. An example is pupal encroachment, a phenomenon in which male butterflies force incompletely metamorphosed female butterflies to enter their chrysalis and force them to mate.

Clint Penick, an assistant professor at Kennesaw State University in Georgia who studies the social lives of insects and was not involved in the research, agrees.

Dr. “The closer we get, the more we find insects fighting each other and drinking each other’s blood,” Penick said. “One of the fun things about studying insects is that you can literally walk out your front door and witness some pretty wild biological interactions on a small scale.”

Mr. Soong and Mr. Tea ask other lepidopterophiles to keep an eye out for more examples of butterfly kleptopharmacophagy and share them with a photo of the behavior at


Source link

Leave a Reply

Your email address will not be published. Required fields are marked *