the Lepidopterous Family Cossidae. 185 



some Mendelian factor. This curious variation is illus- 

 trated in the figure of Thyatira batis, Linn. The hind-wing 

 shows some similarity to that of the Lasiocampidae, 7 

 arises from well before the angle of the cell, and, although 

 there is no anastomosis, 8 is approximated to 7, but there 

 is a well-developed frenulum, and I do not think the 

 similarity points to any real community of descent. Whether 

 the areole is really a primary and not a secondary areole in 

 this family is not quite certain, but I think the former is 

 more probable. 



Geometridae. — This large family affords very interesting 

 studies in neuration. By neuration alone it may be divided 

 into at least five perfectly natural subfamilies. I have 

 figured two of the most primitive genera in the most 

 primitive subfamily Monoctenianae. They show remark- 

 able differences. In Monoctenia there is a slender but 



Fig. 55. — Bupalus piniarus, J. inn. 



distinct branched media in both wings, the areole being 

 absent. In the three Australian genera Diceratucha, Dirce, 

 and Xenogenes the media has been lost, but a large areole 

 and well-marked chorda retained. These are very primi- 

 tive genera, and I have no doubt this is a primitive areole, 

 which in most of the family has been lost. It so happens 

 that veins 10 and 11, which arise from the areocel separ- 

 ately and remain free in Monoctenia, often vary remark- 

 ably, not only in allied genera but in the same genus, and 

 often in different individuals of the same species. This is 

 especially the case in the subfamily Boarmianae. Here 

 10 and 11 may be separate or stalked at origin, and there 

 is a strong tendency for 11 to anastomose with 12 and 10 

 with 9. In Bupalus 11 runs into 12 and 10 anastomoses 

 with 9 to form a secondary areole, which has no relation- 

 ship to the areole present in Diceratucha. In the Geome- 

 trinae 10 is usually stalked with 9 and there is a tendency 

 for 11 to anastomose first with 12 and then with 10, but 



