Fig. 2: Southern border of the army training area in Darmstadt.

Dasypogon diadema was studied intensively during the period of summer 1995 in an area west of Darmstadt, Germany (49°51´N 8°36´E) which was formerly part of a sand-dune area in the upper valley of the river Rhine (`Oberrheintalgraben´). The area covers about 30 hectares and at an alitude of about 110 m and is currently used by the army as a training area. It is enclosed by two motorways (NE and NW) and a Federal Highway in the south.
The surface layer was removed during the 1930s so that the present top soil contains more lime than the neighbouring areas. The area covers a gradation between different plant communities: the peripheral zone and the central part are overgrown with pine trees, the greater part with a dense cover of Phleum arenarium (sand cat's-tail) but a mosaic of open patches is present (Fig. 2). Cezanne (1983) describes approximately 200 higher plants from these patches. A lot of paths run through the area, which contribute to the preservation of sandy places.
The species is common in the Mediterranean region but appears only locally in Germany. It inhabits areas of sparse plant cover in the upper valley of the Rhine and could also be found in north-eastern regions of Germany in the last century. The complete distribution is unclear since Weinberg (1979, 1985, 1986, 1987, 1989, 1991) has described additional species which resemble D. diadema.
Flies were observed and counted over the entire area and notes were made of sex and behaviour. Some studies were performed in the laboratory and some of the described behaviour was recorded using a video camera.
Other asilids recorded in the census area between April and late August 1995 include Antipalus varipes (Meigen, 1820), Choerades ignea (Meigen, 1820), Cyrtopogon lateralis (Fallén, 1814), Dioctria atricapilla Meigen, 1804, Dysmachus trigonus (Meigen, 1804), Eutolmus rufibarbis (Meigen, 1820), Holopogon fumipennis (Meigen, 1820), Lasiopogon cinctus (Fabricius, 1781), Leptogaster cylindrica (De Geer, 1776), Machimus rusticus (Meigen, 1820), Neoitamus socius (Loew, 1871), Neomochtherus geniculatus (Meigen, 1820), Philonicus albiceps (Meigen, 1820), Stichopogon elegantulus (Wiedemann in Meigen, 1820), Tolmerus atricapillus (Fallén, 1814), Tolmerus cingulatus (Fabricius, 1781) and Tolmerus pyragra (Zeller, 1840).