Ru'by-tāil, a.

a. Having the tail or lower part of the body of a ruby color.

Ruby-tail fly (Entom.), one of a family of hymenopterous insects, having a cylindrical body, and the under side of the abdomen of a fiery ruby or copper color, and concave, so that it can be closely applied to the breast, enabling the insects to roll themselves up in the form of a ball when alarmed. Baird.