Moth Drinking Tears From Sleeping Bird's Eye Takes Moth Meme to a New Level

It’s been a big month for moth love, with memes about a lamp-obsessed moth trending hard for weeks. But there’s a new moth in town, and it’s a weird one. In a squirm-inducing video clip published last week by Science Magazine, an erebid moth perches on the head of a black-chinned antbird and drinks from the bird’s eye. As the video’s author explains, though, this thirsty insect is not just being a creep, and this kind of behavior is a lot more common than you might think.

Leandro João Carneiro de Lima Moraes, a biologist at the National Institute of Amazonian Research in Brazil, described this bizarre scene in a paper published September 17 in the journal Ecology. In the paper, Moraes explained that he observed this interaction during a survey about a half hour before midnight on November 4, 2017, in the Brazilian Amazon.

“I found an adult female of Black-Chinned Antbird resting at a branch of understory vegetation in a primary flooded forest,” he wrote. “Approaching, I noticed that this individual has an active erebid moth (G. macarea) located above its neck. This moth was constantly moving its proboscis toward the birds’ ocular area, sometimes resting it inside the eye and presumably feeding upon secretions (tears).” Less than an hour later, he found another black-chinned antbird with another erebid moth drinking its tears.

This tear-drinking behavior, called lachryphagy, is super gross, but it’s also a super normal part of moth behavior. In fact, moths, butterflies, and bees have been frequently observed drinking the sweet, sweet eye liquids of basking reptiles. Moraes’ observation is one of few cases in which moths have been seen drinking the tears of birds.

“This biotic interaction is well reported between moths and mammals, as well as between moths and turtles or crocodiles, but very few events are known involving the interaction between lachryphagous moths and birds,” wrote Moraes.

But why do they do this?

For most moths, this behavior is meant to supplement their diet with nutrients like protein and sodium. In rare cases, entomologists have noted that obligatory lachrypages must feed on tears, but for most of these tear-drinking insects, it’s just like taking a vitamin supplement. Notably, Moraes specifies that these moths are often males.

Research on this behavior has found that males who drink supplemental sodium have higher reproductive success. When these males mate, they actually pass the sodium on to their female partner in the same package that they transmit their sperm cells during mating. Scientists have found that this transmission of sodium can slightly increase the viability of eggs, suggesting that the moths who drink tears may actually enjoy greater reproductive success than those who don’t

And while various species have been observed practicing lachryphagy, not all moths and butterflies — which belong to the order Lepidoptera — benefit from it equally. Some lepidopterans need more sodium than others, while some can’t break down proteins in their gut.

Moraes acknowledges that more research will be required to fully understand this behavior. And just like moths’ attraction to lamps, we have a lot of hypotheses and no solid answers — though it does seem that this behavior is a lot more beneficial to survival than a love of lamps. For now, his observations, the first ever made in Brazil, add to our ever-growing catalog of knowledge about the bizarre habits of these little dudes.