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Not all caterpillars become beautiful butterflies. Some become living milkshakes for their fathers, who swallow the bodily fluids of the caterpillars to entice the ladies.
Recently, scientists reported the first evidence of butterflies sipping from the bodies of caterpillars – dead and alive. They observed adult milkweed butterflies in North Sulawesi, Indonesia, using tiny claws on their feet to scratch wounds from the caterpillars’ bodies so they could lapped up the leaking fluid.
Male butterflies seek out certain compounds produced by milkweed (flowering plants in the Apocynaceae family), which repel predators and help butterflies produce pheromones that attract females. Since caterpillars are stuffed with juices from chewed plants, they make an easy target for butterflies looking to chemically increase their attractiveness to females.
Related: Photos: butterflies cling to involuntary ants
“The larvae of caterpillars would contort rapidly in what appeared to be futile attempts to deter adults from persistent scratching,” said the researchers who observed the baby butterfly drinking. They described their observations in a study published on September 8 in the journal Ecology.
Butterflies in the Danainae family are known as milkweed butterflies because most of the caterpillars in this group feed on milkweed plants, which contain toxic alkaloids which are taken up by the caterpillars and then turned into useful chemicals that protect them from predators. Another use of these alkaloids is in mating pheromones, which are transferred to females in the male’s semen package “as a nuptial gift,” the scientists wrote.
Most milkweed butterfly species are found in Asia, but four species live in North America, including the colorful monarch butterfly (Danaus plexippus), according to the Digital Atlas of Idaho. Male butterflies in this family are known for a unique behavior called leaf scratching, in which adults supplement the sap from plants that they have absorbed as hungry caterpillars by scratching milkweed leaves with their tiny claws to release the sap loaded with alkaloids to drink through their long proboscis. Sometimes males congregate in their hundreds to scratch and sip milkweed leaves, according to the study.
But on December 9, 2019, the study’s lead author Yi-Kai Tea, a doctoral student at the University of Sydney’s School of Life and Environmental Sciences, and co-author Jonathan Soong Wei , a naturalist in Singapore, saw milkweed butterflies in Tangkoko, Indonesia. Batuangus Nature Reserve that scraped another sap-laden source: live milkweed caterpillars.
“Several adults have been observed scratching numerous caterpillars along an expanse of coastal vegetation” that extended over 1,600 feet (500 meters), the researchers reported. They then saw the butterflies actively drinking from “wounded and oozing caterpillars” for hours, with the butterflies sometimes congregating in mixed species groups. Butterflies were so determined to drink caterpillars that even the touch of a human observer couldn’t distract them, the study authors wrote. To describe the behavior, scientists coined the term “kleptopharmacophagy”, which means “consuming stolen chemicals”.
“Alternative neologisms ‘kairopharmacophagy’ (feeding on defensive chemicals from injured caterpillars detected via ‘eavesdropping’) or ‘necropharmacophagy’ (feeding on defensive chemicals from dead caterpillars) might also be appropriate,” reported Researchers.
For three days, scientists counted seven species of milkweed butterflies that scratched and drank alive and dead caterpillars (it is not known whether the dead caterpillars were drunk to death or died of their wounds). One possible explanation why butterflies find caterpillars so delicious is that milkweed alkaloids build up in the bodies of caterpillars from the leaves they eat, making their internal “juices” a more potent and rich in infusion. alkaloids – and therefore more attractive to thirsty males, suggested the scientist.
Butterflies are likely attracted to milkweed leaves already damaged by chewing caterpillars; these caterpillars would be nearby when the adults began to scratch. If a butterfly accidentally scratches a caterpillar, the wound would give off a heady chemical odor that would attract the butterfly and encourage it to scratch the caterpillar even more, according to the study.
Many questions remain about this unusual (and horrific) behavior, for example what specific plant compounds attract butterflies to caterpillars and butterflies in other parts of the world also practice consuming baby, tea said in a press release.
“These simple observations raise questions about the ecology of these well-known butterflies, offering many opportunities for future studies,” he said.
Originally posted on Live Science.
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