The New York Times reports:

The act of breast-feeding is so fundamental to being a mammal that we named ourselves after it. (“Mammalis” translates to “of the breasts.”) But over time, scientists have discovered that other animals also produce nutrient-rich elixirs to feed their young, including flamingos, cockroaches and male emperor penguins.

The latest addition to the cast of organisms that lactate — or something like it — is a species of jumping spider.

Researchers in China have discovered that females of the Toxeus magnus spider secrete a milk-like fluid to feed their offspring. The study, published Thursday in the journal Science, also found the arachnid mothers continue to provide the fluid, which contains about four times as much protein as cow’s milk, well after their spawn had become young adults.

Though the spiders aren’t using mammary glands to produce the fluid, and hence are “lactating” in name only, the findings should prompt scientists to reconsider what they know about nursing and how it evolved, the researchers said.

“Finding such mammal-like behavior in a spider, or in any invertebrate for that matter, was a surprise,” said Richard Corlett, a conservation biologist at the Chinese Academy of Sciences and an author of the study. [Continue reading…]