Micromorphus Mik, 1878

Bickel, Daniel J., 2022, Notes on the genus Micromorphus Mik (Diptera: Dolichopodidae) and the uncertain identity of its type species, M. albipes (Zetterstedt), Zootaxa 5125 (4), pp. 437-444 : 438

Genus Micromorphus Mik

Micromorphus Mik, 1878: 6 . Type species: Hydrophorus albipes Zetterstedt, 1843 , orig. des.

Diagnosis. Small sized (wing length <1.5 mm), often dull brown/ grey coloured species; arista usually dorsal, and often in slight indentation subtended by short ventral projection; dorsal postcranium flat; acrostichal setae absent; 5 dorsocentral setae, sometimes 4; two strong medial scutellar setae only; posterior mesonotum distinctly flattened anteriad of scutellum ( Fig. 2c ); legs rather bare of major setae except for distinct anterior preapicals on FII and FIII ( Fig. 2a ), and TII with strong ad seta and weak pd seta near 1/3; hypopygium usually on elongate peduncle that can be exserted ( Figs 1a, b ); male sternite 8 usually with distinct median dorsoventral sclerotized band ( Figs 1b , 2b ); hypopygial foramen left lateral; epandrium subrectangular; females with tergite 9+10 divided into two acanthophorites, each bearing 4 pointed spines or dornen.

Remarks. Micromorphus comprises some 32 valid species from all zoogeographic regions except Australasia ( Wikipedia contributors, 2021, May 7). Its range includes such widely separated locales as South Africa, Tajikistan, the Philippines, Brazil and Mexico. Although the identity of some species based on females only requires reassessment, undoubtedly more species await description. For example, Negrobov (2000) described eight new Palaearctic Micromorphus species, with four from Tajikistan. This suggests the genus as a whole is significantly more diverse, but possibly overlooked because of its small size and the necessity to clear the male postabdomen for accurate identification. Regarding its position in the higher classification of the Dolichopodidae , Micromorphus has been variously placed in the subfamilies Sympycninae and Peloropeodinae , or is regarded as incertae sedis.

The male postabdomen provides diagnostic structural, setal and cercal characters that enable accurate species identification (e.g., Figs 1a–b , with arrows indicating diagnostic setal positions). Also, it is important to clear the male postabdomen to view the diagnostic structures microscopically, as they may appear obscured in casual macroscopic view (cf. Figs 1a and 2b ). Species in the genus Micromorphus are rather bare of distinctive leg setation and generally lack diagnostic male secondary sexual characters, although two Afrotropical species have flattened tarsomeres on male legs I and II ( Grichanov 2013).

Figures

FIGURE 1. Micromorphus caudatus (Aldrich): a, male postabdomen, ventral; b, male postabdomen, left lateral. M. micidus Parent: c, male postabdomen, left lateral. Legend: cer, cercus; el, epandrial lobe; epand, epandrium; hyp, hypandrium; ph, phallus; st, sternite, tg, tergite; vsur, ventral surstylus. Arrows indicate position of diagnostic setae.

FIGURE 2. Micromorphus caudatus (Aldrich): a, male habitus, left lateral; b, male postabdomen, left lateral; c, female habitus, dorsal; M. micidus Parent; d, female postabdomen, dorsal; e, male habitus, left lateral; f, male wing, dorsal.