Note 23 — Chapter VIII

In regard to the closely analogous case of Spilosoma lubricipeda, Standfuss makes a similar statement. He bred the type on a large scale with the radiate form which he calls intermedia, and says that in four years of miscellaneous crossing he never obtained really transitional forms. Nevertheless after examining large series, especially those of Mr. W. H. B. Fletcher, I came to the conclusion that several might be so classed, but I am quite prepared to find that such specimens are heterozygous. (See Standfuss, Handb. d. Gross-Schmet., 1896, p. 307.) It is by no means unlikely that various dark forms of lubricipeda correspond with a progressive series of factorial additions. Many of the stages have been named, and of these the most definite are the intermedia of Standfuss (probably = eboraci of Tugwell) and the very dark Zatima of Heligoland, in which only the thorax, the nervures and a small field in the fore-wings remain yellow. A form was bred by Deschange from Zatima in which even the field in the forewing is obliterated. The exact circumstances in which Zatima occurs in Heligoland would be worthy of special investigation, for the normal lubricipeda is also found on the island. For references as to the British occurrences see especially, Hewett, W., Naturalist, 1894, p. 353. As to Zatima see especially Krancher, Soc. Ent., II, 1887-8, p. 26. I am indebted to Dr. Hartlaub for information as to the Heligoland types.