Prochyliza Walker 1849

Genus Prochyliza Walker, 1849

Prochyliza Walker 1849: 1045. Type species: Prochyliza xanthostoma Walker 1849, by monotypy.

Diagnosis. The following description of the genus is mainly based on that of McAlpine (1977), with several additions. McAlpine (1977) also provides a key to genera of Piophilidae.

Head. Head higher than long (with the exception of P. xanthostoma). Frons weakly setulose, with 0–2 weak fronto-orbitals, and usually with anterior half or more weakly sclerotized. Ocellar seta and outer vertical seta weak. Ocellar triangle dark, strongly sclerotized. Pedicel about as long as wide; greatly elongated in P. xanthostoma. Vibrissa strongly differentiated. Gena clear orange to black and very deep in height, about half height of eye or more. Posteriorly, gena with a vertical microtomentose strip.

Thorax. Thorax shining black. Mesonotum more or less uniformly densely setulose. Postpronotal and presutural intra-alar setae absent; sometimes one pair weakly developed in P. nigricoxa. Anepisternum setulose. Anepimeron bare. Katepisternal seta very weak to moderately strong. Meropleuron almost completely pruinose.

Wing. Wing usually rather whitish hyaline, veins yellowish to dark brown. Anal vein A1 usually traceable almost to wing margin. Calypters white; margins and fringes brownish in P. inca.

Legs. Coxae, femora, tibiae and tarsi variable in colour. Anterior femur with series of relatively strong posterior setae. Mid tibia with a brush of long, yellowish hairs at the posterovental apical part and hind coxa with a comb of short, stout setae in males of P. lundbecki.

Abdomen. Male abdomen with tergite 5 little longer (less than 0.5 times) than tergite 4; sternite 5 slightly broader than sternite 4. Male postabdomen asymmetrical; sternites 6 and 7 more or less fused. Margin of sternite 7 with a posteriorly directed peg-like process. Epandrium with 2–3 long, strong setae arising posterodorsally and several additional setae throughout the surface; in P. i n c a also with a pair of small but conspicuous horn-like spines. Surstylus very reduced, with the appearance of a small lobe. Pregonite bearing 1–2 setae. Phallus very long and haired. Female abdomen with a clear, empty area in the middle of sternite 7. Ovipositor bearing three pairs of long setae and some additional short setulae. Morphology of the ovipositor very similar to that of other genera of the subtribe Piophilina, as illustrated by Zuska & Laštovka (1965). Females with two elliptical spermathecae (Sturtevant 1926).

Immature stages. Larvae breed mainly on carrion, including human corpses (Martín-Vega 2011), but also recorded infesting decaying vegetables (Duda 1924), fruit (Webb & Graham 1956) and proteinaceous products from the food industry (Zuska & Laštovka 1965). Third-instar larvae show the typical skipping behaviour observed in other species of Piophilidae (Bonduriansky 2002; Martín-Vega et al. 2012). The morphology of the immature stages (egg, larval instars and puparium) has been described for P. nigrimana (Martín-Vega et al. 2012). See Martín-Vega et al. (2014) for a key to the larvae of Piophilina genera.

Remarks. Prochyliza was originally proposed by Walker (1849) as a monotypic genus including the species P. xanthostoma. Consequently, the description of the genus was strictly focused on the unique features of that species, i.e. the unusually long head and the very elongated pedicel. Melander & Spuler (1917) redescribed both the genus Prochyliza and the species P. xanthostoma, highlighting a wide variability in the shape of the head of this species, with some specimens showing a globular head and very short antennae. Subsequently, Melander (1924) described a new species in this genus, P. brevicornis, from those latter specimens with non-elongated head and antennae. For his part, Duda (1924) described the subgenus Liopiophila within genus Piophila, combining under it the species P. nigrimana, P. nigricornis, P. nigricoxa, P. lundbecki and L. varipes. Duda (1924) also suggested that Prochyliza should be also considered as a subgenus of Piophila, because of the few differences between Prochyliza and Piophila (including Liopiophila) females. Finally, McAlpine (1977) ranked Liopiophila as a genus containing a single species, L. varipes, and redefined the genus Prochyliza using distinctive characters different from the elongated head and pedicel, which remained as the distinctive characters of P. xanthostoma. As a result, McAlpine (1977) also assigned to Prochyliza the species P. lundbecki, P. nigricornis, P. nigrimana and P. nigricoxa, included until then in genus Piophila, and described two new species: P. azteca and P. inca. The genus would thus include eight species. Given that the current paper describes a new one, but also invalids the name P. nigricornis, the number of known species for genus Prochyliza remains on eight.

It must be mentioned that Ozerov (2004), in his fine revision of the classification of the family Piophilidae, considered the genus Liopiophila Duda as a junior synonym of Prochyliza, thus including its single species, Liopiophila varipes (Meigen), in genus Prochyliza. According to Ozerov (2004), the presence of one or several hair-like setae on the anepimeron of L. varipes would be the only character which differentiates genus Liopiophila from Prochyliza and, therefore, he did not consider it enough to distinguish Liopiophila as a separate genus. I respectfully disagree with his suggestion as Liopiophila shows other distinctly different characters from Prochyliza: the gena is significantly narrower than that of Prochyliza and more similar to that of Stearibia, being clearly lower than half eight of eye, and the surstylus is long and slender in lateral view, but reduced to a small lobe in Prochyliza. Also importantly, Liopiophila larvae shows ventral creeping welts equipped with two rows of spines and anterior spiracles with the lobes arranged in two groups like the larvae of genus Stearibia (Martín-Vega et al. 2014), whereas in Prochyliza larvae the creeping welts are equipped with three rows of spines and the anterior spiracles show the lobes arranged in a single group like the larvae of genus Piophila (Martín-Vega et al. 2012; Paños et al. 2013). In his proposed phylogeny for the Piophilidae, McAlpine (1977) suggested that Prochyliza would be the sister group of genus Piophila, whereas Liopiophila and Stearibia would conform a different monophyletic group. I agree with this hypothesis, given the similar morphology of male genitalia and postabdomen in both Piophila and Prochyliza genera (McAlpine 1977), as well as the larval features shared between these two genera on one hand (Martín-Vega et al. 2012; Paños et al. 2013), and between both Liopiophila and Stearibia genera on the other hand (Martín-Vega et al. 2014).

Below I suggest an updated key to the described species of genus Prochyliza, partially based on that from McAlpine (1977). The current key considers the variability in the body colouration characters of P. nigrimana, complementing them with non-colouration-based diagnostic characters. A synopsis compiling the most relevant information available for each species, with a detailed description of a new species and a redescription of P. nigrimana, are provided after the key.