Above, this fine native bumble bee was caught pillaging a thistle blossom in a small slot side-canyon of Lower Hot Springs Canyon on April 25, 2011. The morning air was still cool (for which reason the bee was slow-moving enough to be still-captured at fairly close range) and a thistle plant was actually blooming here after a very poor spring rainy season, because the sandy soil of the slot canyon at this point had retained more moisture than the floodplains below.
Main sources: O'Toole, Christopher & Anthony Raw, 1991, Bees of the World, London: Blandford; Batra, Suzanne, 1984, "Solitary Bees", Scientific American 250:2:120-27; The Bee Works (thanks to Dr. Stephen Buchmann); Buchmann, Stephen & Gary Nabhan, 1996, The Forgotten Pollinators, Washington DC: Shearwater Books.
Below, roughly at their true relative sizes, at left: European Honey Bee; center: Carpenter Bee -- 30-40 mm long; right: silk-making bee -- 4 mm long. This should provide a sense of the range of sizes attained by bees of various species around the world. The world's smallest known bee -- Perdita minima, only 2 mm long, is found in the vicinity of Tucson.
Bees are members of the insect order Hymenoptera, membership in which they share with the wasps and the Ants. (Hymenoptera are defined literally by their "membrane wings", of which they have two pairs, the forewings larger than the hindwings. In flight, these wings are linked together by tiny hooks.) Like the ants, bees developed from a line of non-social stinging ("aculeate") wasps -- in the case of bees, mud-dauber wasps (Family Eumenidae?), but unlike wasps (who collect insect prey for their larvae), bees collect nectar and pollen for their larvae. Bees rely for their food on pollen and nectar, and their females have pollen-collecting structures on their legs and bodies. Since the evolutionary emergence of bees depended on the existence of flowers, the earliest bees must have appeared during the Cretaceous period, when flowering plants became the dominant vegetation on earth (between 146 million and 76 million years ago). The oldest known bee fossil is preserved in tree amber from the New Jersey Upper Cretaceous of 96-74 Mya.
While most Americans think mainly of socially specialized honeybees (fertile queen, sterile workers, semipermanent hives) when they hear the word "bees", Tucson alone has about 1,000 species of bees, and some 99% of these are solitary -- each female builds a separate nest which contains the cells for her own offspring. These varieties of solitary bee play very important roles in pollinating the plants of our area, and these are the kinds of bees we will focus on here. First we provide an introduction to Solitary Bees, then more detailed information on some particular bees of our area, including the type of bee which pollinates Saguaro Cactus flowers.
Below, a Carpenter Bee on a budding Datura flower, photographed on the floodplain of the Middle San Pedro River, September 1, 2008: