When the "Yukimushi" or "snow bugs" gently dance in Hokkaido's autumn sky, many people feel that the first snow of the season is just around the corner. But "Yukimushi" isn't their official name. What exactly are these creatures? And is the common rumor among Hokkaido residents that "when the snow bugs fly, the first snow will fall" actually true? We'll reveal the truth in an easy-to-understand way.

The True Identity of the Snow Bug is the "Todononeoowatamushi"

What is commonly called the "Yukimushi" is actually a type of aphid called "Todononeoowatamushi" (Prociphilus oriens). As adults, they are covered in waxy, white, cotton-like fibers and fly aboutふわふわ, which led to them being called "snow-like bugs" or "Yukimushi."

The Todononeoowatamushi are born in spring on Yachidamo trees (Manchurian ash) and move to Todomatsu trees (Sakhalin fir) from summer to early autumn. They feed on the sap of the Todomatsu firs, going through several generations within a year. In late autumn, the winged adults migrate back to the Yachidamo trees. So, what we see as flying snow bugs are actually adult Todononeoowatamushi in the middle of their migration from Todomatsu to Yachidamo trees.

A Peculiar Survival Strategy for a Weak Insect

The Todononeoowatamushi is known as a "weak insect." It has no means to defend itself against predators and is easily preyed upon. However, it has a remarkable counter-strategy: a form called the "stem mother."

Through repeated molting, a female becomes a "stem mother." This female then gives birth to female larvae that are clones with the exact same genes, and these larvae, in turn, produce more clones. A single female can produce about 150 larvae, so by reproducing faster than they are eaten, they have managed to survive.