Sicus is a small but distinctive genus within the family Conopidae, represented in Europe primarily by the species Sicus ferrugineus. Flies of this genus are medium-sized and immediately recognisable by their uniform reddish-brown to chestnut coloration, which sets them apart from the more boldly patterned conopids. The head is large and rounded, typical of thick-headed flies, and the abdomen is elongate and slightly constricted at the base.

Adults are most frequently encountered on flowers, especially in woodland edges, clearings, and hedgerows, where they feed on nectar and often resemble small solitary bees. The larvae are endoparasitoids of bees, with females laying eggs directly into adult hosts using a short, stout ovipositor ⓘ. Sicus exemplifies the quieter, less conspicuous end of conopid diversity, combining subtle mimicry with a highly specialised parasitoid ⓘ life cycle.