The BVD stands for Back Vertex Distance, this is a measurement that is included on any prescription where the sphere or cylinder powers are higher than + or - 5.00D and to a lesser extent some prescriptions where it is less than this power.
Winged Drone | Alate | Male Ant. Drones are the only male ants in a colony. They are born from un-fertilized eggs. Drones are not like typical ants. They donât do any work in their nests, and they look more like wasps than ants. They are reproductive winged ants and so are alates.
Figure 1. Carpenter ant castes-left column winged female (top), winged male-right column-workers of varying sizes. Carpenter ants are among the largest ants in Minnesota. There are several species of carpenter ants that may be found infesting homes and other buildings. Normally workers are black, or red and black, in color; and range in size from 3/8 to Â½ inch. Winged queen ants may be as large as one inch. However, size is not a reliable characteristic for identifying carpenter ants. In Minnesota, there is one species with workers no larger than 3/16 inch.