Colletidae is one of the most species-rich families within the clade Anthophila, holding roughly 2,000 individual species. They're a primitive group of bees, meaning that they were probably one of the first groups to diverge from the wasps. They're solitary, so provide and care for their young alone. They can be small or large; hairy or hairless, most species possessing short tongues. They get their names from their nesting behaviour. These bees secrete liquids from their mouths, plastering the walls of nest cavities. They are present worldwide, however, are particularly prevalent in South America and Australia. They carry pollen in the crop, which is a modified part of the digestive system used to store food. As a group they are described as docile, seldom stinging those which come close to them.