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.
In early spring or late winter people often encounter these large black ants in homes. These big ants are different than the more common small, brown nuisance ants that plague kitchens. The big ants are called carpenter ants (Camponotus spp.) and unlike their smaller cousins, nest above ground in cavities. Nest building and cavity expansion by these large, powerful ants can cause damage if nests occur in our homes. Most of the ants you find in homes are small, less than 1/4, and brown. There are several species of small brown ants that can nest in our home's walls or nearby soil and enter homes in search of food and water (see House Ants for identification and control). Nuisance ants are just that, a nuisance.