Urocerus japonicus, commonly known as the Japanese horntail, is a species of sawfly, native to southeastern Asia.

Studies show that the dispersal distance of the female is higher than the male.

When ovipositing, the horntail introduces a symbiont fungus which either provides essential nutrients for the larvae, or which produces enzymes which help decompose the lignin or cellulose in the wood.

[5] The horntail carries arthrospores of the fungus in a pair of small sacs on the abdomen known as "mycangia".

A newly emerged adult female makes a short dispersal flight before drilling several holes in the bark of a suitable tree, depositing eggs and arthrospores from the mycangia in each hole.