Simulium (Simulium) xanthinum Edwards, 1933

Crosskey, Roger W. & Crosskey, Margaret E., 2000, An investigation of the black ¯ y fauna of Andalusia, southern Spain (Diptera: Simuliidae), Journal of Natural History 34 (6), pp. 895-951 : 934-935

23. Simulium (Simulium) xanthinum Edwards

Spain references: Edwards (1933, original description), GonzaÂlez PenÄa (1990, as gaudi ), Crosskey (1991), GonzaÂlez (1997).

Andalusia records

Authors’ material. Site 21: 44 larvae. Site 25: 5 pupae. Site 27: 1m (1), 4 larvae. Site 34: 1 pupa, 13 larvae. Site 116: 1 larva. Site 117: 4 larvae. Site 118: 2 pupae, 28 larvae (18.v.1986). Site 119: 3 pupae, 18 larvae (18.v.1986), 8 pupae, 68 larvae (31.v.1986). Site 120: 1 pupa, 1 larva (31.v.1986), 31 larvae (8.iv.1994), 9 larvae (23.iii.1996). Site 121: 34 larvae (1.viii.1974), 1 pupa, 3 larvae (18.v.1986), 31 larvae (31.v.1986), 9 larvae (23.iii.1996). Site 122: 31 larvae. Site 123: 1m (1), 37 larvae. Site 124: 1 pupa, 55 larvae. Site 126: 1 pupa, 38 larvae. Site 127: 1 pupa. Site 128: 1m (1), 7 pupae, 126 larvae. Site 129: 4 larvae. Site 130: 31 larvae (31.vii.1974), 112 larvae (9.iv.1994). Site 131: 37 larvae. Site 136: 3 land 5m (7 exuviae together on substrate piece, one lwith individual exuviae) [one m given to Zoological Institute, St Petersburg], 5 pupae, 39 larvae (15.iv.1997).

Other specimens seen. Simulium xanthinum holotype m, CaÂdiz Province, Algericas , 12± 20.v.1925 (H. Zerny) (Naturhistorische s Museum, Vienna) .

Previous reports. Crosskey (1991) recorded the Andalusian specimens found in 1974 and 1986 (data here reincorporated into the list of authors’ material above).

Remarks

This little-known species is of localized occurrence in southern France, northeastern and southern Spain and Morocco (type locality of its synonym S. gaudi Grenier and Faure ). In Andalusia it occurs only in the source region of the RõÂo Guadalquivir and in the Serrania de Ronda. The species is very distinctive in all life stages: adults are predominantly orange-yellow, the pupal gill has six very black ®laments con®gured rather three-dimensionally (®gure 43), the cocoon is of loosely corbicular type (®gure 42) and living larvae have a pure lime-green colour. Early stages are found in highly alkaline watercourses where substrates (and even the pupal cocoons) are heavily incrusted with calcareous deposits. Larvae are rendered extremely conspicuous on their substrates by their unusual colour. The lime-green colouring is evidently locked in the haemolymph since chromatocytes are apparently absent and the colour vanishes very soon after collection into alcohol. A complete taxonomic account of the species has been provided by Crosskey (1991).