414 LEPIDOPTERA CHAP. 



Neither is the geographical distribution limited by this inferior 

 condition of .the most important of the organs of locomotion, for 

 Cheimato'bia brumata (the Winter-moth) one of the species with 

 flightless female, is a common and widely distributed Insect in 

 Europe and North America. 



Although the classification of this family is based almost 

 entirely on wing-nervuration, yet there are some divisions of the 

 Geometridae in which this character is remarkably variable, 

 certain individuals frequently exhibiting considerable abnor- 

 mality. 1 Amphidasis bct-ularia is believed to have changed its 

 variation considerably in the course of the last fifty years. Pre- 

 vious to that time a black variety of the species was unknown, 

 but it has now become common ; and it is believed that other 

 species of Geometridae are in process of exhibiting a similar 

 phenomenon. 2 



Fam. 37. Noctuidae (Owlet -Moths, Eiden of the Germans). 

 -This very extensive assemblage consists of moths rarely seen 

 in the day-time, of generally sombre colours, with antennae desti- 

 tute of remarkable developments in the male (except in a small 

 number of forms) ; proboscis and frenulum both present ; a com- 

 plex sense-organ on each side of the body at the junction of the 

 metathorax and abdomen. The number of species already known 

 can scarcely be less than 8000 ; owing to their large numbers 

 and the great general resemblance of the forms, their classifies-, 

 tion is a matter of considerable difficulty. Although the peculiar 

 structure at the base of the thorax was long since pointed out, 

 it has never received any thorough investigation. Few other 

 remarkable structures have yet been discovered: the most in- 

 teresting is perhaps the peculiarity in the hind wings of the 

 males of certain Ommatophorinae recently pointed out by Sir 

 G. F. Hampson 3 : in the genera Pcttula and Argiva the form of 

 the hind wings is normal in the females, but in the male the 

 anterior one-half of each of these wings is aborted, and the 

 position of the nervures changed ; this condition is connected 

 with the development of a glandular patch or fold on the wing, 

 and is remarkable as profoundly affecting a structure which is 



1 For a table, see Meyrick, I.e. 



2 Barrett, "Increasing Melanism in British Geometridae," Ent. Monthly Mag. 

 1895, p. 198. 



3 P. Zool. Soc. London, 1892, p. 192. 



