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Insects of Britain and Ireland |
Figs. 1–4, Alcis repandata (Mottled Beauty). Figs. 1–2, pale form: Ilfracombe, June 1912. Figs.3–4, melanics: Leek, Staffs, June 1952. The melanic forms predominated in the Leek district during the decade 1948–1958, in rural habitats located only 10 and 30 miles from heavily indistrialized Stoke-on-Trent and Manchester, to the extent that pale specimens were never encountered. Figs. 5–8, Peribatodes rhomboidaria (Willow Beauty). Fig. 8 typifies the dusky aspect of all the individuals of this common species encountered in the Leek district in the decade 1948–1958. The situation apparently reflected displacement of the light (normal) form by f. perfumaria, which existed as a relatively rare rural melanic prior to the Industrial Revolution. For comparison, Figs. 5–7 represent material collected at one locality in France in 1953, where the pale form (Figs. 5–6) was predominant, but one fully melanic specimen (f. rebeli, Fig. 7) was also encountered.
Figs. 1–2, Ilfracombe (Devon), 1912. Figs 3–4, Leek (Staffs.), 1952. Figs. 5–7, Bagneux, Seine, France, July 1953; Fig. 8, Leek, Staffs., July 1949.>
Geometridae: Ectropis crepuscularia (Small Engrailed) and Odontopera bidentata (Scalloped Hazel)
Figs. 1–2, Ectropis crepuscularia (Small Engrailed): rural to industrial melanism. In the decade 1948–1958, melanic individuals (e.g., Fig. 2) of this common inhabitant of deciduous woodland predominated in the Leek district, in ostensibly rural habitats located 10 and 30 miles from industrial Stoke-on-Trent and Manchester. The photo at left portrays one of only two specimens of the light form that were encountered there during that time.
Figs 3-7, Odontopera bidentata (Scalloped Hazel). This species has been interpreted as exhibiting industrial melanism of a polygenic type in Britain, exhibiting enhanced duskiness in response to environmental pollution (Ford, 1955; Majerus, 1998, 2002). Individuals were commonly attracted to light in deciduous woodland around Leek during the decade 1948–1958, when all the specimens collected were relatively dark. They are exemplified here by Figs 3 and 4 (males) and 5 (female), alongside a ‘normal’ 1908 female from Folkestone (Fig. 6). The heavily melanic f. nigra, which was not encountered in the Leek district in those years, is illustrated (Fig. 7) by an old specimen from Huddersfield.
Agriopis leucophaearia (Spring Usher), A. marginaria (Dotted Border), A. aurantiaria (Scarce Umber): polymorphism and melanism. Specimens of all three species were commonly found resting on tree trunks by day, in mixed deciduous woodland around Leek, N. Staffs, from 1948–1958. Localities ostensibly rural, but about 10 and 30 miles miles from the heavily industrial regions of Stoke-on-Trent and Manchester.
Figs. 1–6, Agriopis leucophaearia (Spring Usher): exemplifying male colour variants (including non-industrial melanism) of this common, polymorphic species, of which the lighter forms were numerically predominant. Figs. 7–9, A. aurantiaria (Scarce Umber): 2 typical males and (9) a female. By contrast with the other two representatives of this genus (and with Erannis defoliaria, q.v.), the Scarce Umber is not noticeably polymorphic, and melanism is either absent or very rare. Figs. 10–16, A. marginaria (Dotted Border): 3 light (‘normal’) males, 3 melanics, and an apparently melanic female. Light and melanic forms (the latter supposedly representing non-indistrial, rural melanism) were equally common, without obvious intermediates. Fig. 14 is a 1911 specimen from Ilfracombe (Devon, R.A. Nichols coll.), for comparison with Figs. 11 & 12.
Angerona prunaria (Orange Moth), light and melanic forms
Light and rural melanic forms respectively of male (1 & 2) and female (3&4). The species is dimorphic throughout its range, the pale form being commoner although the dark form is genetically almost completely dominant (Ford, 1955). Seemingly exemplifying rural, non-industrial melanism.
Specimens collected by S.G. Smith at Castor Hanglands (Northants.), 1954.
Epirrita dilutata (November Moth), pale and melanic forms
The species was commonly beaten from oak in the decade 1948–1958, when the extreme industrial melanic form shown here was quite uncommon despite proximity of the locality to heavily industrialized Stoke-on-Trent and Manchester (10 and 30 miles respectively).
Specimens collected November 1959, Ballington Wood, Leek, Staffs.
Erannis defoliaria (Mottled Umber), males and a (wingless) female. Exemplifying colour variants in the males, all commonly represented in the population of a small area of deciduous woodland during the decade 1948–1958. Although the locality lies within 10 and 30 miles respectively of heavily industrialized Stole-on-Trent and Manchester, it is doubtful whether the dark forms reflected any drift to industrial melanism from the normal polymorphism exhibited by this species in unpolluted habitats.
Specimens from Ballington Wood, Leek, Staffs. (L. Watson).
Revised 12 February 2019