Pegomya meridiana

Michelsen, Verner, 2009, Taxonomic revision of the Pegomya meridiana species group (Diptera: Anthomyiidae) including natural enemies of invasive Hypericum spp. (Clusiaceae), Zootaxa 2299, pp. 29-43 : 30-31

The Pegomya meridiana species group

The Pegomya meridiana species group is proposed for three Palaearctic species: P. meridiana (Villeneuve) , P. provecta (Villeneuve) and P. canariensis Michelsen. These are very small to medium-sized anthomyiids with body and legs dark-coloured, atypical for species of Pegomya . Hennig (1976a) did not consider P. meridiana and P. provecta as closely related, as he tentatively placed the first species together with P. tabida (Meigen, 1826) and related species feeding as larvae on fresh boletes ( Boletaceae ), while he placed P. provecta in a different, more vaguely defined species group named after the ubiquistic fungivorous P. geniculata (Bouché, 1834) . Griffiths (1983) did not mention P. provecta but improved on Hennig’s classification of P. meridiana by moving the species to his ‘ Pegomya rubivora section’ that contains about all Pegomya species with phytophagous larvae other than the leaf mining ones. The same year a new Canarian endemic species, P. canariensis was described by Michelsen (in Michelsen & Báez (1985). It was considered most closely related to P. provecta based on similarities in the male terminalia, but also P. meridiana was tentatively added to this group of species. New morphological and biological evidence presented below corroborates the idea that these three species form a monophyletic group:

Female spiracles VI situated within the lateral margins of tergite V behind spiracles V ( Fig. 9 ). Such pronounced forward displacement of spiracles VI is a unique character state not previously reported from any Anthomyiidae . Only in female kelp-flies of the genus Fucellia Robineau-Desvoidy are these spiracles situated near at or exceptionally within the lateral hind margins of tergite V ( Hennig 1966; Suwa & Darvas 1998).

Oviscapt distally laterally compressed, forming a pointed cutting edge by the apically closely aligned epiproct and cerci (e.g., Figs. 10 , 20 , 30 ). A compressed oviscapt is also seen in the SE Palaearctic and N Oriental Pegomya chinensis species group (e.g., Suwa 2000), but those species are much larger and have the cutting edge formed alone by the projecting apices of the cerci.

Larval development in the floral parts or (rather) seed-capsules of Hypericum spp. has only been confirmed for one species ( P. meridiana ), but plausibly applies to other members of the P. meridiana species group. This is supported by field observations suggesting that the shrub Hypericum canariense is a larval host plant of the likewise Canarian endemic anthomyiid P. canariensis (see below).

Further, a sister-group relationship between P. provecta and P. canariensis is supported by: spiracles VII absent in both males ( Fig. 15 ) and females ( Figs. 22 , 31 ). Again, this appears to be a unique character state not previously reported from the Anthomyiidae . Pegomya meridiana has retained the anthomyiid standard configuration with spiracles VII in the asymmetrical sclerites of the male pregenital segments VII+VIII ( Figs. 3, 4 ) and in tergite VI of the female ( Fig. 9 ).

Figures

FIGURES 9 – 12. Pegomya meridiana (Villeneuve), female terminalia. 9. Abdominal segments V and VI, right half in internal view showing spiracles V – VII. 10. Oviscapt, lateral. 11. Distal part of same, dorsal. 12. Oviscapt, flat-mounted. Same scale. Abbreviations: ce = cerci, ep = epiproct, hy = hypoproct; sp = spiracle; V – VIII = abdominal segment numbers.

FIGURES 20 – 23. Pegomya provecta (Villeneuve), female terminalia. 20. Oviscapt, lateral. 21. Distal part of same, dorsal. 22. Oviscapt, flat-mounted. 23. Spermatheca and duct. Same scale. Abbreviations: ce = cerci, ep = epiproct, hy = hypoproct, VI – VIII = abdominal segment numbers.

FIGURES 30 – 34. Pegomya canariensis Michelsen, female terminalia. 30. Oviscapt, lateral. 31, 32. Basal and distal segments of oviscapt, flat-mounted. 33, 34. Distal oviscapt, lateral and dorsal. Different scales for 30 – 32 and 33, 34. Abbreviations: ce = cerci, ep = epiproct, hy = hypoproct, VI – VIII = abdominal segment numbers.

FIGURES 13 – 19. Pegomya provecta (Villeneuve), male terminalia. 13, 14. Sternite V. 15. Asymmetrical pregenital sclerites of segments VI – VIII showing spiracles VI (arrows). 16, 17. Hypopygium. 18. Pre- and postgonites. 19. Phallus. Same scale.

FIGURES 1 – 8. Pegomya meridiana (Villeneuve), male terminalia. 1, 2. Sternite V. 3. Asymmetrical pregenital sclerites of segments VI – VIII showing left spiracles VI and VII. 4. Ditto, showing right spiracles VI and VII. 5, 6. Hypopygium. 7. Pre- and postgonites. 8. Phallus. Same scale. Abbreviations: sp = spiracle, VI, VII = abdominal segment numbers.