The main goals or our study are to identify apid bees (Apidae), determine their flight times, and quantify their abundances in different habitats in Dyke Marsh Wildlife Preserve (DMWP), part of the national park George Washington Memorial Parkway, Northern Virginia, based on Malaise-trap sampling. The species-rich bee family Apidae is one of five bee families in DMWP, and this family includes Apis (Honey Bees), Bombus (Bumble Bees) Ceratina (Small Carpenter Bees), Xylocopa (Large Carpenter Bees), and many other genera. The 267-hectare Preserve comprises part of the Potomac River, flood-plain and swamp forests, and the largest remaining freshwater, tidal marsh in the Washington, D.C., Area. In 1996, we started a long-term arthropod survey in DMWP and operated six Townes-style, floating Malaise traps, with two in the marsh, flood-plain forest, and their ecotone from April 1998 – December 1999.
The Malaise samples contain 816 apid bees in 33 species and morphospecies, including eight social species, six solitary species, and eight cleptoparasitic species and morphospecies of other bees. As a group, the bees flew from 20 March – 6 December. In species with at least 16 specimens per year, we found that the cleptoparasites Nomada electella and N. imbricata were statistically more common in the forest than the ecotone or marsh in 1998. Three out of seven trap samples of solitary-bee species with 21–85 specimens were statistically female biased. The sampling obtained two species of rare Mid-Atlantic cleptoparasitic bees. Our apid bee sample is the first such sample taken in DMWP and any other U.S. freshwater tidal marsh to our knowledge. The sample is baseline information regarding the DMWP ecosytem and can help the National Park Service manage DMWP in view of global change and our world-wide pollinator crisis.