Interfrontal setae

In the stem-species pattern of the Milichiidae, there is a paired row of interfrontal setulae on the frontal vitta. This is a plesiomorphic character state for the Milichiidae, because in the stem-species pattern of the Chloropidae there is probably a row of three or four interfrontal setulae too (Nartshuk 1987), and in the Carnidae there is a row of two or three interfrontal setulae. The stem-species pattern of the Acartophthalmidae is unknown: in Acartophthalmus bicolor the interfrontal setulae are unevenly distributed on the frons (fig. 189 in Hennig 1958) and in A. nigrinus there are no or up to three interfrontal setulae present. Within the Schizophora, interfrontal setulae which form two rows on the frons are present for example in Sphaeroceridae and Tethinidae. The rows may therefore be plesiomorphic for the Chloropidae family-group.
The anteriormost interfrontal setula is called the supra-antennal seta. It stands next to the ptilinal fissure, is pro- and medioclinate, and is often stronger than the other interfrontal setulae. Between the supra-antennal seta and the eye margin there is a further small proclinate setula at the anterior margin of the frons in the Milichiidae. This setula is an apomorphy for the Milichiidae because it is absent in the Chloropidae, Acartophthalmidae, and Carnidae. Within the Milichiidae the setula is secondarily lost in Aldrichiomyza, in Microsimus, and in the stem-species of a group comprising the Milichia speciosa-group+Pholeomyia and maybe Ulia.
In the stem-species pattern of the Milichiidae, there is a paired row of interfrontal setulae on the frontal vitta. This is a plesiomorphic character state for the Milichiidae, because in the stem-species pattern of the Chloropidae there is probably a row of three or four interfrontal setulae too (Nartshuk 1987), and in the Carnidae there is a row of two or three interfrontal setulae. The stem-species pattern of the Acartophthalmidae is unknown: in Acartophthalmus bicolor the interfrontal setulae are unevenly distributed on the frons (fig. 189 in Hennig 1958) and in A. nigrinus there are no or up to three interfrontal setulae present. Within the Schizophora, interfrontal setulae which form two rows on the frons are present for example in Sphaeroceridae and Tethinidae. The rows may therefore be plesiomorphic for the Chloropidae family-group.
The anteriormost interfrontal setula is called the supra-antennal seta. It stands next to the ptilinal fissure, is pro- and medioclinate, and is often stronger than the other interfrontal setulae. Between the supra-antennal seta and the eye margin there is a further small proclinate setula at the anterior margin of the frons in the Milichiidae. This setula is an apomorphy for the Milichiidae because it is absent in the Chloropidae, Acartophthalmidae, and Carnidae. Within the Milichiidae the setula is secondarily lost in Aldrichiomyza, in Microsimus, and in the stem-species of a group comprising the Milichia speciosa-group+Pholeomyia and maybe Ulia.
In Desmometopa and some Pholeomyia and Phyllomyza species, the row of interfrontal setulae is emphasised by sclerotisations at the base of the setulae and the development of microtrichiae. In such cases the rows are called interfrontal stripes. Interfrontal stripes are an apomorphic character for Desmometopa, but according to Sabrosky (1983) there are several unnamed Neotropical species without interfrontal stripes (but with interfrontal hairs) that may belong to Desmometopa. According to Sabrosky, this condition may be a reduction of the interfrontal stripes (from Brake 2000).