Psilidae is family of two-winged flies. Commonly called the rust flies, there are at least 38 species in 4 genera. The Carrot fly (Chamaepsila rosae) is a member of this group.They are found mainly in the Holarctic.
For terms see Morphology of Diptera Small or medium-sized (1.5 mm.-10 mm.) flies with a slender body.They are yellow to reddish, brown or black coloured. Head is spherical with (relatively) small eyes and the face is often slanted backward.The antennae are small or with the third antennal segment conspicuously elongate.The arista has short or long pubescence. The postvertical bristles are divergent or absent.Ocelli and ocellar bristles are present.Vibrissae are always absent. There are 0-2 pairs of frontal bristles and scattered interfrontal setulae. The costa is interrupted at some distance from R1 and only the basal part of the subcosta is developed. The vein bordering the anal cell is straight on the outer side. Crossvein BM-Cu is present and the cell cup is closed. The wing is usually clear to slightly tinged but in some cases along costa, the wing tip or the cross-veins there are dark bands. The wing has a transverse weakening in the basal half. Tibiae are without a dorsal preapical bristle. See  Description and plates from Francis Walker'sInsecta Britannica Diptera.
Psilidae are especially common in cool places on low dense vegetation. This explains why the family is well represented in temperate zones. The larvae are almost exclusively phytophagous on non-woody plants. They live either in stems, tubers or roots. A few species live under tree bark.Some form galls. Several species are pests in agriculture and horticulture. Chamaepsila rosae Fabricius, and Psila nigricornis Meigen are instances.
Hennig. 1941. Psilidae.In: Lindner, E. (Ed.). Die Fliegen der palaearktischen Region 5,41,1-38. Keys to Palaearctic species but now needs revision (in German).
Séguy, E. (1934) Diptères: Brachycères. II. Muscidae acalypterae, Scatophagidae. Paris: Éditions Faune de France 28. virtuelle numérique
Shtakel'berg, A.A. Family Psilidae in Bei-Bienko, G. Ya, 1988 Keys to the insects of the European Part of the USSR Volume 5 (Diptera) Part 2 English edition.Keys to Palaearctic species but now needs revision .