Information: Sitaris muralis was described by Förster in 1771 originally as Necydalis muralis.
Sitaris muralis is a rare species with a black body and yellow coloration at the base of the elytra (the coloration can be variable). Females have shorter antennae than males. The elytra are separated at the base (near the pronotum), tapering toward the rear, and do not cover the membranous hind wings. The abdomen of females enlarges when filled with eggs (though not to the extent seen in the genus Meloe). The larvae (triungulins) are black.
Body length: 8 - 10 mm
Peak activity: June - August (depends on region)
Remarks: Sitaris muralis is a Western European species with its distribution center in the Mediterranean region. Its occurrence is confirmed from Portugal and England (though it is absent in Scandinavia and the Baltic states), extending through much of southern and central Europe to Ukraine and the southern parts of European Russia.
In the Czech Republic, it is a rare and highly localized species, typically found in lowlands and foothill regions. Due to its secretive lifestyle and late seasonal appearance, it is likely to be frequently overlooked.
Adults of Sitaris muralis appear relatively late in the season, from the end of July to September, with peak activity occurring between mid-August and early September. When conditions are favorable, adults may be observed in large numbers—dozens to hundreds—within small areas. When disturbed, they exhibit thanatosis, falling motionless to the ground and feigning death for several seconds.
The species naturally inhabits vertical, sun-exposed earthen or loess walls in xerothermic environments, such as eroded banks or slopes. As a secondary habitat, it can also be found on masonry structures made of soft building materials, such as unfired clay bricks. All such habitats are colonized by Sitaris muralis only in the presence of its hosts—solitary bees of the order Hymenoptera.
The larvae, known as triungulins, are specialized parasites of solitary bees from several genera, including Anthophora, Andrena, Colletes, Eucera, Halictus, Nomada, and Osmia. Females lay sticky eggs in August directly at the entrance of bee nest cavities. In April, the newly hatched triungulins cling to the hairs of emerging bees and are carried into the nest, where each larva occupies a single brood cell. Initially, it consumes the bee egg, then feeds on the nectar and pollen provisions. It then transforms into a worm-like second instar larva, which continues to consume the host's food reserves. The new generation of Sitaris muralis emerges in late summer.
Distribution: 
Taxonomic classification:
Material examined (& observation):
Our observation period: June ~ August
Sampling Methods: on bush and flowers 
CzechiaSitaris muralis (Forster, 1771)
