Community ecology of bee flies (family Bombyliidae)
Bee flies are most diverse in arid regions, specifically on sandy substrates.
In the 1970's, I was intrigued at such high diversity under extreme physical
conditions, counter to the conventional wisdom about gradients of species
diversity. Bee flies use insects that burrow in sand as hosts for
their larvae and seasonally abundant flowering annual and perennial plants
as sources of 
nectar
and pollen for adults. Here a female Lordotus pulchrissimus
feeds on the perennial composite shrub,. rabbitbrush
(Chrysothamnus nauseosus). She is an older female, about 10-15 days
from emergence as you can see from her faded color; she is one of the 200
female flies that I marked in a demography
study that I did in 1986. This population occurs on the semi-stabilized
parabolic sand-dunes on the north shore of Mono Lake. Sand
dunes have the peculiar property that they store water because
of the low water-holding capacity of sand, allowing plants access to deep
soil moisture when plants on surrounding clay and silt substrates are well
into the summer's evapotransipiration deficit. This abundance of water
in sand-dune habitats causes sand-dune plants and arthropods dependent
on them to have larger population sizes and higher species diversity.
From 1978 to 1982, I surveyed bee-fly communities in the major California
Deserts particularly in the Mojave (dunes on the Death Valley floor, higher
elevation shrubsteppe at Harrisburg Flats and on the Darwin Plateau) and
in the Great Basin (dunes on the north shoreline of Mono Lake). The
bee-fly community in sand dunes around Mono Basin were less diverse than
those in Mojave and Colorado deserts. Adult bee flies did not appear
to be limited by nectar availability at the Mono Basin site, in constrast
to the Mojave desert sites. Evidence included: bee flies at
the Mono Basin site occurred in lower densities per flower but not per
unit area; bee flies exhibited a lower frequency of feeding, a lower degree
of specialization on different available flower species, and less pronounced
phenological changes as resource abundance changed during the season, compared
to the Mojave desert sites.
Publications:
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Toft, C.A. 1983. Community patterns of nectivorous adult parasitoids (Diptera, Bombyliidae) on their resources. Oecologia 57:200-215. PDF
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Toft, C.A. 1984. Resource shifts in bee flies (Diptera: Bombyliidae): Interactions among species determine choice of resources. Oikos 43:104-112.22. PDF
Related studies:
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Kimsey, L.S., R.B. Kimsey and C.A. Toft. 1981. Life history of Bembix inyoensis (Sphecidae, Hymenoptera) in Death Valley. Journal of the Kansas Entomological Society 54:665-672.
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Toft, C.A. and L.S. Kimsey. 1982. Habitat and behavior of selected Apiocera and Rhaphiomidas (Diptera, Apioceridae), with descriptions of immature stages of A. hispida. Journal of the Kansas Entomological Society 55:177-186.
 Toft
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