Dasypogon diadema is common in Southern Europe, where it inhabits different habitats. Adamovic (1971a, b) found it on steppes, partly eroded hilly slopes, sandy hollows, weedy grass plots, Christ´s thorn shikara and on grassy foothills. Cloudsley-Thompson (1960) found it on dunes at the Atlantic coast. The author has found it also in dry meadows, pastures, olive groves, and clearings in Southern France and the Alps. The more adverse climat in Germany restricts its distribution to xerothermous places, which are present in the upper valley of the Rhine. In addition the soil must be sandy to facilitate oviposition. D. diadema is therefore usually found in former sand-dune (a result of the last glacial period) areas. Most of these have been destroyed by agriculture and development during the present century.
Dasypogon diadema is found mainly on the open areas at Darmstadt, usually on bare patches or somewhat overgrazed areas. During the midday heat some specimens (mainly males) can also be found in wooded areas. The temperature rose above 44°C on soil (3 p.m., 8 July 1995), 36°C in the shadow, and 33°C inside the vegetation (10 cm above the ground). The flies could therefore be frequently observed inside the vegetation.