MALACOSOMA. 523 



judge from the distribution of the normal form and the large number 

 of closely allied species directly evolved therefrom, is the predominant 

 species. We suspect, however, that 21. neustria and its very closest 

 allies are the most newly developed forms, whilst the polymorphic M. 

 castrensis appears to be, in some respects, the more ancestral. The 

 imago of the latter species shows the generalised basal oval mark, 

 commencing on the costa of the forewings and curving round to the 

 thorax, although occasional specimens have this mark developed into 

 a well-defined, moderately straight basal line, reaching to the inner 

 margin as in 21. neustria and its offshoots. (21. azteca from Vera Cruz 

 has also the curved basal line.) The sexual dimorphism of the species 

 of this genus is most marked, and the dark rust-red or red-brown 

 unicolorous females of 21. neustria, M. castrensis, 21. alpicola and 21. 

 franconica are so similar, that it is somewhat difficult to refer certain in- 

 dividuals to their proper species, and one is inclined to suspect this female 

 type to be the ancestral form of the genus. 21. alpicola and 21. franconica 

 are both evidently specialised offshoots of 21. castrensis, 21. alpicola 

 having a similar curved generalised basal mark on the forewings, 

 whilst in 21. franconica it appears to cross to the inner margin although 

 it is frequently lost before reaching the edge of the wing. This 

 character of franconica is maintained in hybrid castrensis x franconica 

 bred by Standfuss, in which particular the examples follow franconica 

 and not castrensis. A fine dark male of 21. castrensis in the British 

 Museum coll. (Frey coll.) gives an excellent clue as to the line taken in 

 the specialisation of the dark coloration of alpicola and franconica, for 

 the olive-brown shading that largely covers its wing is not at all 

 unlike the final tint reached in these species. 21. alpicola and 21. 

 franconica are very closely allied, but 21. alpicola is much more densely 

 scaled in both sexes, the male is darker, the transverse line better 

 developed, the basal line somewhat curved, the hind wings also densely 

 scaled, and with a pale shade — all characters that place it near 21. 

 castrensis. The male of 21. franconica is almost transparent over the 

 greater part of the area of the wings, the fasciae are almost obsolete, 

 the outer fascia commences nearer the apex, the nervures are darker, 

 and the transverse shade of the hindwings is lost in the transparency of 

 the discal area, whilst the males of both species retain the chequered 

 fringe of 21. castrensis. The females of both are unicolorous, those of 

 alpicola more dense, and vary from orange-red to deep red-brown 

 (rarely with indistinct markings traceable), whilst those of franconica 

 are more uniformly tinted in rust-brown, much more translucent, and 

 thinly scaled. In most respects both species much more nearly 

 resemble 21. castrensis than 21. neustria, although all are really very 

 close. 



The "neustria " group is an exceedingly interesting one, the species 

 with sufficient similarity to make any but an expert doubt their specific 

 distinctness. Thus 21. calif arnica has a fine brick-red male, with 

 yellowish base and a yellow outer transverse line edging the median 

 band, the female being yellowish ; 21. americana males are of a deep 

 red-brown colour with grey transverse lines, and those of 21. tfisstria 

 of a brighter red, with a fairly defined but only slightly darker median 

 band (in some cases unicolorous). 21. azteca (from Mexico) is another 

 well-defined, dull, grey-brown species that might easily be considered 

 a strong local race of 21. neustria, except for the direction of the 



