Generally, flowers have developed specialized mechanisms for pollination by a specific class of species, the exclusion of other species is a crucial aspect of the flower’s specialization1. However, certain bee species display foraging behaviors such as nectar robbing in which they bite tiny holes in the flower, usually near the base of the corolla. From which the bee can then access the nectar without having the necessary evolutionary traits adapted to that particular flower species. Thus, the nectar produced to attract the intended pollinator is taken without any interaction with the flowers reproductive organs greatly decreasing the chances of a successful cross pollination. In most circumstances the nectar robber lacks the morphological traits needed to access the nectar from within the flower, a short proboscis (tongue) is often the limiting factor. Nectar robbers can be subdivided into two categories, primary and secondary robbers. Primary robbers being the individuals whom make the original hole to extract the nectar and secondary, which are the individuals whom obtain nectar via the hole made by the primary robbers1.
1. Bentley B, Elias TS. The Biology of Nectaries. New York, NY: Columbia University Press; 1983. https://books.google.com/books?hl=en&lr=&id=9ULQh89IINgC&oi=fnd&pg=PA153&dq=nectar robbing bees&ots=qQvKS2iWZd&sig=8FUWN3CE7c8z5SrTTz1z4Df7OMY#v=onepage&q&f=false