Remember when the only milk was milk? Like, from a cow. Then came soy milk, almond milk, cashew milk, rice milk, etc. While most people wouldn’t need a whole lot of nudging to experiment with any of these milk imitators, a more recently discovered "milk" may require some time to catch on.
Yes, cockroach milk.
Diploptera punctate, or the Pacific beetle cockroach, is the only cockroach that gives birth to its offspring directly, rather than by depositing a pod or an egg. The cockroach feeds its young in-utero with a milk-like crystal substance.
According to a study published in the International Union of Crystallography in July 2016:
A single crystal is estimated to contain more than three times the energy of an equivalent mass of dairy milk. This unique storage form of nourishment for developing embryos allows access to a constant supply of complete nutrients.
However, according to Inverse, getting the milk is rather laborious:
Scientists carve out the cockroach’s midgut with a scalpel to harvest the milk, which actually is more the consistency of crystals ... At around 40 days old, the cockroach begins to lactate (enjoy that image) for its offspring, and thus opens the window for the scientists to get up in there, which involves killing the cockroach. The process is fairly straightforward and inexpensive, but it’s not feasible for mass production just yet...
So, perhaps calling it "cockroach milk" is a bit of a stretch as it won’t be sitting next to cow’s milk in the dairy aisle anytime soon (or ever). Still, the thought is enough to send a slight chill up your spine.