Also known as “Polyester Bees”, Colletids are hugely varied in appearance, but have a common two-lobed tongue. Furthermore, all Colletids secrete a cellophane-like substance with which they line their brood cells. This creates a waterproof nest, which allows Colletids to nest in flood areas, such as stream banks. The most common visitor to Echinacea of the Colletidae family is in the genus Hylaeus. (Mader et al. 219)
(Mader et al. Attracting Native Pollinators: Protecting North America’s Bees and Butterflies. 2011. The Xerces Society.)