(Taxonomic note. This species is a good example of evolution and dynamic biogeography in action. After the last ice age, North African (Saharo-Arabian) conditions appear to have extended north across the Mediterranean Sea and into southern Europe, and with it the distribution of Hyles tithymali. About 3,600 BP, Europe appears to have suddenly cooled, with Mediterranean climatic conditions pushing south across the Mediterranean Sea to the coasts of North Africa and Middle East. This appears to have allowed the more cold-adapted Hyles euphorbiae to expand westwards into Europe from the Iranian Plateau, replacing and absorbing northern populations of H. tithymali as it did so. However, relict populations of H. tithymali survived on several semi-isolated Mediterranean islands, such as Madeira, Sicily, Malta and Crete. In southern Italy and on Sicily, H. tithymali has managed to resist the southward expanding population of H. euphorbiae to some extent, as evidenced by the occurrence of what appear to be pure H. tithymali-like larvae as far north as Naples (P. Mazzei, pers. com.). On the more isolated islands of Crete (Meerman & Smid, 1988) and Malta, the populations are still recognizably H. tithymali, but a steady low-level influx of H. euphorbiae seems to have diluted these to some extent to form hybrid populations (Hundsdoerfer et al., 2005b).)
GB: Barbary Spurge Hawkmoth, F: Sphinx du Tithymale
Deilephila tithymali Boisduval, 1834, Icones hist. Lepid. 2: 30.Type locality: Canary Islands.
Holarctic; western Palaearctic region. Pleistocene refuge: Monocentric -- Canary Island subsection of the Mediterranean refuge. Part of the present day Macronesian faunal element.
Wingspan: 60--85mm. Many individuals resemble subsp. mauretanica, with which it undoubtedly shares a common ancestor. Quite distinct from Hyles euphorbiae: median stripe of forewing narrow and cream in female, broader and silver in male, many having superimposed silver venation. Not as variable as H. euphorbiae.
Restricted to the Canary and ?Cape Verde Islands, where it is widespread, occurring from sea-level to 1000m in short-lived but well-defined colonies (Schurian & Grandisch, 1991). Commonest in the drier and warmer parts, such as steep-sided valleys (van der Heyden, 1988) and cultivated areas where its main hostplant is most abundant. Behaviour identical to that of Hyles euphorbiae; attracted to the flowers of Bougainvillea and light (van der Heyden, 1991; 1988).
Unlike for H. e. euphorbiae, this subspecies tends to be active after midnight, with females calling and pairing between 01.30 and 03.00 hours (Harbich, 1994). This pattern of behaviour is also found in H. t. gecki (de Freina, 1991) and H. t. deserticola (Staudinger, 1901), supporting the amalgamation of these subspecies into a species group distinct from H. euphorbiae.
Continuous-brooded throughout the year, although scarce from May to August (van der Heyden, 1990, 1991).
OVUM: Very similar to that of Hyles euphorbiae, but with a noticeable bluish hue. Laid in clusters of up to 25 on the growing tips of smaller hostplants, hatching four to eight days later.
LARVA: Full-fed, 70--80mm. Almost identical to those of subsp. mauretanica and subsp. deserticola.
Young larvae are black at first, turning to olive black after feeding, with the final colour pattern appearing in the third or fourth instar. Fully grown, it is quite unlike any colour form of H. euphorbiae, more closely resembling certain varieties of H. livornica. In some individuals, the white eye-spots may be flushed with red.
Eggs and small larvae are generally found on small plants of Euphorbia regis-jubae (van der Heyden, 1991). Larger larvae move to and then feed quite openly on the taller, more mature bushes, alternating frenzied bouts of feeding with long stretches of basking (Pittaway, 1976). They may occur in such numbers as to defoliate large areas of hostplant. In midsummer some individuals become fully grown in 20 days.
Being continuous-brooded, various stages of development can be found simultaneously on the same plant, although larvae are scarce from July to October (van der Heyden, 1991).
Major Hostplants. The shrubby Euphorbia regis-jubae (van der Heyden, 1988) and Euphorbia lamarckii [syn. E. broussonetii & E. obtusifolia]. (It should be noted that as E. regis-jubae is confined to Gran Canaria, Fuerteventura and Lanzarote, E. lamarckii is utilized on the other islands.)
Minor Hostplants. Euphorbia paralias & E. segetalis (Gil-T., pers. comm. 2008).
PUPA: As H. euphorbiae, but with many pupae diapausing for two or more years, a characteristic of species adapted to desert conditions. Usually killed by sub-zero temperatures.
None recorded.
The Canary Islands, including Lanzarote (van der Heyden, 1996).
Extra-limital range. The Cape Verde Islands, off the west coast of Africa. However, the exact taxonomic position of this population is uncertain.
Interestingly, H. t. deserticola has been reported from the island of Fuerteventura, Canary Islands, by Gil-T. (2002) and Eitschberger & Saldaitis (2006). However, the illustration given by the latter is of a pale, desertic ecotype of H. t. tithymali, a condition probably caused by feeding on Euphorbia paralias growing on hot, dry sand dunes (Hundsdoerfer, Kitching & Wink, 2005a). Additionally, a molecular phylogenetic study of the population places it firmly within H. t. tithymali (Hundsdoerfer, Kitching & Wink, 2005a). Although it may be possible for individuals of H. t. deserticola to occasionally cross the 100km of water between Morocco and Fuerteventura, there is (as yet) no genetic evidence for this.
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