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.
Ants are social insects and are divided up into three castes: workers, males, and queens (figure 1). Workers are sterile, wingless females which range in size from 1/20 inch long to about 1/2 inch long. The workers of some ant species vary in size and are divided into major (large) and minor (small) workers. Ants vary in color from yellow to red to brown and black and various combinations of these. Like all insects, ants have three distinctive body parts: head, thorax, and abdomen. All ants have a pair of elbowed (bent) antennae on the head and a constricted area between the thorax and abdomen called the petiole. The petiole has either one or two nodes (bumps) (figure 2).