Subfamily Azeliinae Robineau-Desvoidy, 1830

A subfamily of ‘lower’ Muscidae including the former Achanthipterinae Hennig, 1962 (Kutty et al. 2014). Species from nine of a total of 12 recognized genera were examined (Table 1).

• Achanthiptera Rondani, 1856

The only known species, Achanthiptera rohrelliformis (Robineau-Desvoidy, 1830), has vein C extensively setulose ventrally and bare dorsally (state A4).

• Potamia Robineau-Desvoidy, 1830

Both examined species, Potamia littoralis Robineau-Desvoidy, 1830 and P. setifemur (Stein, 1916), have vein C extensively setulose ventrally and bare dorsally (state A4).

• Australophyra Malloch, 1923

The only known species, Australophyra rostrata (Robineau-Desvoidy, 1830), has the ventral costal setulae confined to CS1 (state A2).

• Azelia Robineau-Desvoidy, 1830 (Fig. 5A–B)

A total of 10 species was examined. They all have vein C bare ventrally (state A0), as shown by Azelia cilipes (Haliday, 1838) (Fig. 5A–B).

• Drymeia Meigen, 1826 (Fig. 6A–C)

A large, morphologically varied genus found primarily in the northern and elevated parts of the Holarctic region. More than 10 examined species of Drymeia, including some unidentified ones, agree with Azelia in the absence of ventral costal setulae (state A0), as shown by D. vicana (Harris, 1780) (Fig. 6A). One species, D. hamata (Fallén, 1823) (Fig. 6B–C), differs by having vein C extensively setulose ventrally (state A4).

Ventral setulae are also seen on CS 1 in Drymeia tetra (Meigen, 1826) and some D. alpicola (Rondani, 1871), but these are setulae displaced from the lower anterior spinule-setula row.

• Hydrotaea Robineau-Desvoidy, 1830 (Fig. 7A–C)

Examination of a large number of species showed that vein C is bare dorsally and with a trend towards loss of ventral costal setulae.

Two species, Hydrotaea cyrtoneurina (Zetterstedt, 1845) (Fig. 7A) and H. ringdahli Stein, 1916, have vein C extensively setulose ventrally (state A4).

The following species have ventral costal setulae confined to CS1 (state A2): Hydrotaea anxia (Zetterstedt, 1838), H. cyaneiventris Macquart, 1851, H. dentipes (Fabricius, 1805) (Fig. 7B), H. hirticeps (Fallén, 1824), H. militaris (Meigen, 1826), H. palaestrica (Meigen, 1826) and H. similis Meade, 1887 .

Some species have ventral setulae on less than the basal half of CS1 (state A1): Hydrotaea capensis (Wiedemann, 1818), H. chalcogaster (Wiedemann, 1824), H. diabolus (Harris, 1780) and H. ignava (Harris, 1780) .

Most species examined are without ventral setae on vein C (state A0): Hydrotaea aenescens (Wiedemann, 1830), H. borussica Stein, 1899, H. cinerea Robineau-Desvoidy, 1830, H. floccosa Macquart, 1835, H. irritans (Fallén, 1823), H. glabricula (Fallén, 1825), H. meridionalis Portschinsky, 1882, H. meteorica (Linnaeus, 1758) (Fig. 7C), H. pandellei Stein, 1899, H. pellucens Portschinsky, 1879, H. penicillata

(Rondani, 1866), H. pilipes Stein, 1903, H. pilitibia Stein, 1916, H. scambus (Zetterstedt, 1838), H. tuberculata Rondani, 1866 and H. unispinosa Stein, 1898 .

In Hydrotaea borussica, H. irritans and allied species, the lower anterior spinule-setula row on the basal part of CS1 consists of setulae only, some of which are frequently displaced ventrally.

• Neohydrotaea Malloch, 1924

The only examined species, Neohydrotaea lundbecki (Michelsen, 1978), has vein C bare dorsally and extensively setulose ventrally (state A4).

• Thricops Rondani, 1856

Examination of a large number of species revealed that most of them have vein C bare dorsally and extensively setulose ventrally (state A4): Thricops aculeipes (Zetterstedt, 1838), T. beckeri (Pokorny, 1893), T. culminum (Pokorny, 1889), T. cunctans (Meigen, 1826), T. foveolatus (Zetterstedt, 1845), T. furcatus (Stein, 1916), T. genarum (Zetterstedt, 1838), T. hirtulus (Zetterstedt, 1838), T. innocuus (Zetterstedt, 1838), T. longipes (Zetterstedt, 1845), T. nigrifrons (Robineau-Desvoidy, 1830), T. nigritellus (Zetterstedt, 1838), T. rostratus (Meade, 1882), T. semicinereus (Wiedemann, 1817), T. separ (Zetterstedt, 1845), T. septentrionalis (Stein, 1898), T. simplex (Wiedemann, 1817) (males), T. spiniger (Stein, 1904), T. sudeticus (Schnabl, 1888), T. tomkovichi Vikhrev in Vikhrev & Sorokina, 2009 and T. vaderi Savage, 2003 .

Females of Thricops simplex tend to have a short, irregular row of dorsal costal setulae on CS2 and adjacent basal part of CS3 (state A6).

A more extensive row of dorsal costal setulae on CS2 and CS3 (state A7) is seen in Thricops albibasalis (Zetterstedt, 1849), T. lividiventris (Zetterstedt, 1845) and T. rufisquamus (Schnabl, 1915) (only female examined).

In Thricops diaphanus (Wiedemann, 1817), the dorsal costal setulae tend to occupy CS1‒3 (state A8), although bare patches distally on CS1 and on CS2 do occur in some males.

• Huckettomyia Pont & Shinonaga, 1970

A small, exclusively northern Palaeartic genus. The single male of Huckettomyia watanabei Pont & Shinonaga, 1970 examined is extensively setulose on the dorsal side of vein C (state A8).