The notion of suck has its etymological origin in the Latin word I will free. The concept is often used to refer to what people do insects to the sip nectar of the flowers.
Nectar is called sugary substance that produce the nectaries. The nectary, meanwhile, is a gland that have certain flowers.
The bees and other animals, in this framework, are in charge of sucking the nectar to feed themselves. This means that they gently suck on this juice. For flowers, the production of nectar is vital to attract insects that then carry out the pollination (the transfer of pollen).
Let us take the specific case of bees. To be able to suck, the specimens have a proboscis, a kind of language of great extension. At the same time, they have mouthparts that favor said suction. Depending on the length of the proboscis, the different types of bees are in a position to suck, or not, nectar from certain flowers: if the tongue is short, the sucking action is only possible in those flowers that have an open corolla.
Arriving at a flower, the bees taste the quality of nectar. When the nectar is according to their needs, they continue to go to that kind of flower to sip.
At colloquial language, on the other hand, one speaks of libar with respect to savor a liquor or other drink. A person who is dedicated to sucking something, what he does is savor it. For instance: “My father taught me that you have to drink the liquor, not drink it in a hurry”, “In the restaurant they offered me a small glass to drink the new wine from the San Roque winery”, “You shouldn’t drink rum during working hours”.