Phytobia Lioy, 1864

Lonsdale, Owen, 2021, Manual of North American Agromyzidae (Diptera, Schizophora), with revision of the fauna of the " Delmarva " states, ZooKeys 1051, pp. 1-481 : 1

Phytobia Lioy

Phytobia Lioy, 1864: 1313. Type species: Agromyza errans Meigen 1830: 178, by monotypy. Spencer 1969: 101; Spencer and Steyskal 1986b: 73; Zlobin 2007a: 57, 2007b: 47, 2008a: 67, 2008b: 61.

Dendromyza Hendel, 1931: 22 [as subgenus of Dizygomyza ]. Type species: Agromyza carbonaria Zetterstedt 1848: 2739, by original designation. Kangas 1935: 1 [as genus]. Frick 1952a [synonymy].

Liomyzina Enderlein, 1936a: 180 [nomen nudum - no type species designated]. Frick 1952a [synonymy].

Liomycina Enderlein, 1936b: 42 [attributes to Enderlein 1936a]. Type species: Domomyza lunulata Hendel 1920: 124, by original designation. Syn. nov. [all previous synonymies of the genus name described in the paper are misspelled " Liomyzina ", that is, the nomen nudum given in Enderlein (1936a)]

Shizukoa Sasakawa, 1963: 38. Type species: Shizukoa seticopia Sasakawa 1963: 41, by original designation. Spencer 1965d [synonymy].

Phytobia is a genus of relatively large and stout-bodied species found in shrubs and trees as larvae. The larvae feed on young xylem, incorrectly referred to as “cambium” in much of the literature ( Ylioja et al. 1998). These larvae are far less obvious to the collector compared to those in other genera feeding within leaves or even stems, and as such, biological data are incomplete for many species. This method of larval feeding is essential to the definition of the genus, as external adult morphology broadly overlaps with those of other genera, and has historically resulted in a broad fluxuation of it boundaries. Zlobin (2007a) suggested that Phytobia likely consisted of at least three separate genera, and while structures of the distiphallus do appear to support a deep split between several main lineages, the relative uniformity of external adult morphology, commonalities of the remainder of the male genitalia, and the complex, unique larval habit suggest otherwise, although little can be stated with any certainty until more is learned about this understudied group.

Phytobia can be easily confused for some Agromyza , but the latter always has an apical bend on vein R1 in Nearctic species, and the lateral margin of the first and second tergite has a conspicuous file. The relatively common Nemorimyza posticata is also superficially similar, but in this species the fore tibia has a lateromedial seta, and the lunule is semi-circular and silvery (not shallow and yellow to brown with a light pruinosity); N. maculosa is also similar, but it has a dark spot on the halter.

Zlobin (2007a, 2007b, 2008a, 2008b) noted that nearly 100 species have been described in this genus, but this likely far underrepresents its actual diversity. Sixteen species are known in the United States and Canada, including Spencer and Steyskal’s (1986b) "Sp. n. Salix " from New York. Five species occur in the Delmarva states. Contrasting other groups of Agromyzidae , many species show a relative uniformity in genitalic morphology, leaving external characters such as colour, chaetotaxy and venation to predominate in keys and diagnoses.