Andrena crataegi

Justification:
The Hawthorn Mining Bee is a solitary bee that occurs across most of the United States and Canada, with most records from the northeastern United States. The species apparently does not occur in the grassland dominated center of the United States and gene flow between two fairly isolated portions of its range is not well understood. Using all records, the extent of occurrence for the species is 9,342,347 km2, and recent records are numerous and relatively well distributed throughout the range of the species. The species occurs in forests and shrublands, as well as urban and agricultural areas. It is an important pollinator of apple crops. Across the range of the species, impacts from exposure to pesticides, climate change, and habitat degradation and loss have been observed. These threats may be acting on species at local levels. However, because the species is widespread, occurs in many habitat types, and uses pollen from specious and abundant plant genera, it is unlikely that it is threatened with extinction at this time. As such, it is assessed as Least Concern.

The Hawthorn Mining Bee is a dietary generalist that exhibits some preference for pollen from the plant family Rosaceae, with many records of this species foraging from the genus Spiraea (Laberge 1969). It is an important pollinator of apple crops in the eastern United States (Danforth et al. 2019). It has been observed in evergreen and deciduous forests, shrubland, urban areas, and agricultural areas, This species nests underground, and has been observed nesting communally (Osgood 1989). Observations from bee emergence suggest that this species is proterandrous, with males emerging before females. Nests are often reused by females year after year, and can have multiple entrances. Of the four nests excavated in the most comprehensive study of the species’ biology, cells numbered from 29 to 54. Nest cells were located at the end of lateral burrows, and were lined with a waxy Dufour’s gland secretion (Osgood 1989) that serves to both isolate the provision from pathogens in the surrounding soil and to regulate water uptake from the soil atmosphere (Cane and Love 2021). Most cells were located at a depth of about 38 cm (Osgood 1989). Females provision each cell with a ball of pollen moistened with nectar on which they lay a single egg (Michener 2007). Records of this species come from March to September, with most records from May and June (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019). Parasitic bees from the genus Nomada have been observed emerging from nests of the Hawthorn Mining Bee (Osgood 1989).

Specific threats to this species have not been thoroughly investigated. Because of its prevalence in agricultural areas, it may be at increased risk of pesticide exposure in agricultural areas. It may also be impacted by pesticide use in horticultural settings as well. In a study of pesticide residues in pollen at ornamental plant nurseries, one of the common sources of pollen for this species (Rosaceae: Spiraea) was found to have the greatest acute toxicity of pesticide residues, including both thiamethoxam and clothianidin, which are both highly toxic to bees (Stoner et al. 2019). Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena crataegi is a ground nesting species, and nests may be harmed by certain agricultural practices such as tilling, which can kill bees nesting close to the surface (Williams et al. 2010). Additionally, Andrena have been reported to have low reproductive output because of the short adult life span, and a low rate of brood cell provisioning (reviewed in Danforth et al. 2019). Other threats to bees generally include habitat loss or modification, climate change, pesticide use, exposure to pathogens from managed bee species, and competition with honey bees (Brown and Paxton 2009; Potts et al. 2010; Wojcik et al. 2018; Grab et al. 2019; Raven and Wagner 2021).

Conservation needs No known conservation actions are in place for this species. Observations of this species are known from Bureau of Land Management (BLM), United States Forest Service, National Park Service, Department of Defence, Tribal, and U.S. Army Corps of Engineer land, but this does not confer any specific protections to the species. Further research is needed to determine the overall size of the population and to identify trends and existing threats. This species has been ranked using NatureServe criteria at the global level as Secure (G5), and several states and provinces as Secure (S5) or Apparently Secure (S4). Specific conservation needs for this species have not been identified. Due to the importance of supporting wild bee populations for pollination services, general conservation practices are recommended including, restoring, creating, and preserving natural high-quality habitats to include suitable forage and nesting sites; limiting pesticide use on or near suitable habitat, particularly during the adult bee’s flight period; promoting farming and urban practices that increase pollinator-friendly plants in margin space; minimizing exposure of wild bees to diseases transferred from managed bees; and lastly, avoiding honey bee introduction to high-quality native bee habitat.

Surveys targeting this species are needed throughout its range to determine its persistence throughout its historic range. More information is needed about the population status, range limits, habitat, and ecology of this species.

(a. any taxonomic concerns about the validity of the species? b. any taxonomic revisions underway that would require a species reassessment.