Everyone can remember learning about mammals in preschool and early gradeschool. We were taught that only mammalian animals produce milk for the purposes of nourishing their offspring. While this is not exactly accurate due to the many non-mammalian lifeforms that also produce milk, it was good enough at the age of six. However, many people may be surprised to learn that a spider species has recently been discovered that produces its own nourishing fluid for its suckling spiderlings. This spider species is known as Toxeus magnus, and it is also notable for looking exactly like an ant in order to fool predators.
The Toxeus magnus is a species of jumping spider that is native to southeast Asia. Female spiders of this species produce a fluid containing sugars, fats, and proteins in order to provide their babies with nourishment. The lead researcher investigating this new spider species, biologist Rui-Chang Quan of the Chinese Academy of Sciences, is referring to this fluid as “milk” for the time being, as such a substance has never been found before. Interestingly, researchers learned that the spiderlings continue feeding on their mother’s milk well into maturity, which is unusual.
While spiders are not known for producing their own milk, a female spider’s parenting behavior is quite similar to mammalian parenting behaviors. Although many spider species are naturally solitary, many female spiders provide extended care for their offspring. For example, some female spiders avoid eating in order to constantly guard their egg cases, and other females will open their egg cases in order to give their spiderlings an occasional ride on their back. Other females even regurgitate food for their young, like birds do, but the recently discovered species of spider developed the ability to produce nourishing milk. Much like mammals, Toxeus magnus spiderlings are entirely dependent on their mother’s milk for survival. The researchers that found this spider species are convinced that many other spider species exist that also produce milk for their young, only they have yet to be discovered.
Do you know of any insect species that produce milk for their offspring?