Phthorima Förster 1869

Klopfstein, Seraina, 2014, Revision of the Western Palaearctic Diplazontinae (Hymenoptera, Ichneumonidae), Zootaxa 3801 (1), pp. 1-143 : 76-77

Phthorima Förster 1869

Phthorimus Thomson 1890

Type species. Bassus compressus Desvignes 1856

Diagnosis. Females of Phthorima can readily be identified by their strongly compressed metasoma and concave hind margins of the tergites in combination with a closed fore wing areolet. Males are more difficult to separate from some species of Homotropus , but their face is distinctly less coriaceous and with smooth and shining areas between the distinct punctures.

Face coriaceous and matt but with some shining areas and distinctly punctate, without vertical impressions, in females entirely black or with a yellow central patch, in males entirely yellow. Clypeus with apical margin thin, except in P. picta with a preapical impression rendering basal three-quarters concave. Antenna with apical flagellomeres longer than wide, in males with linear, narrow tyloids, without long setae. Mesoscutum without notauli; smooth and shining, strongly punctate, yellow shoulder marks present or absent; mesopleuron smooth and strongly punctate, especially on lower half; epicnemial carina complete ventrally. Propodeum with a full set of carinae enclosing basal, petiolar and lateral areas, or with carinae partly reduced; propodeal spiracle inconspicuous; scutellum only carinate basally. Fore wing areolet present, but vein 3rs-m often unpigmented; hind wing with 2–4 basal hamuli. Hind tibia orange or brown, or white with subbasal and apical brown bands in P. p i c t a. Female metasoma strongly compressed from apex of third segment, knife-like, tergites 3 to 6 with hind margins concave, extending further back laterally than dorsally; tergites without transverse impressions. First tergite with median dorsal carinae, if present, broadly separated. Second tergite with spiracle dorsal, above lateral fold, third tergite with spiracle usually above but sometimes below the fold. Metasoma black or obscurely brown. Ovipositor sheaths 0.3 times as long as hind tibia, parallel-sided and fully enclosing ovipositor. Males with tergites 9 and 10 as separate sclerites, sternite 9 about 1.5 times wider than long, emarginated apically, thus forming two lobes, their outer corners rounded.

Phylogeny. Phthorima clustered with Bioblapsis in a molecular phylogenetic analysis, in a clade also including some Homotropus species. However, this grouping was not strongly supported. More data and denser taxon sampling are needed to confirm the monophyly and closest relatives of this genus. Morphologically, the genus is rather uniform, with P. pict a being the most distinctive species.

Distribution. Holarctic. Besides the four Western Palaearctic species, two have been described from the Eastern Palaearctic and five have been recorded from the Nearctic only.

Biology. All reliable host records for this genus are from the syrphine tribe Pipizini ( Fitton & Boston 1988).

Key to species

1. Malar space with a deep subocular sulcus ( Fig. 21 A). Clypeus with a subbasal impression rendering the apical three-quarters concave ( Fig. 21 A). Male with tyloids on flagellomeres 6 or 7 to 10 or 11. Hind tibia whitish with subbasal and apical light brown bands.................................................................. Phthorima picta (Habermehl)

- Malar space with subocular sulcus absent or present only as coriaceous sculpture ( Fig. 21 B). Clypeus with a subapical impression, rendering the basal three-quarters convex ( Fig. 21 B). Male with tyloids at least on flagellomeres 7–14/15. Hind tibia orange or brown...................................................................................... 2

2. Propodeum with carinae incomplete; basal and petiolar areas not enclosed by full set of carinae. Scutellum usually marked with yellow. Fore and mid coxae in females often yellow............................ Phthorima xanthaspis (Thomson)

- Propodeum with carinae distinct, delimiting basal and petiolar areas. Scutellum often black but sometimes yellow, especially in males. Coxae in females orange or black................................................................. 3

3. Second metasomal tergite at least 1.5 times longer than basally wide, punctate only to middle, second half smooth or only very sparsely punctate, the punctures separated by several times their diameter. Third tergite with punctures restricted to anterior margin, front half smooth and shining. Coxae usually entirely orange but sometimes black...................................................................................................... Phthorima compressa (Desvignes)

- Second metasomal tergite shorter than or as long as wide, punctate almost to apex and with second half finely sculptured and matt. Third tergite coriaceous sculpture and densely punctate over entire length of tergite. Coxae black........................................................................................... Phthorima obscuripennis (Hedwig)

Figures

FIGURE 21. Faces of Phthorima species showing the grove in the malar space and the shape of the clypeus. A. Phthorima picta. B. Phthorima compressa. Scale bars represent 500 µm.