312 Mr. A. R. Wallace o;i 



antennae of tlie strong-winged Callidnjas. Tlie cliief cliflTerence 

 from the usual arrangement is in placing Terias before P'tcris 

 and after Felder's new genus Elodina, which has hitherto been 

 divided between Pieris and Terias. 



The portion of my work to which I have devoted most time 

 and attention has been the proper determination of the sexes in 

 many species of Pieris which have hitherto never been properly 

 located, and the separation of the heterogeneous mass of species 

 in that genus into natural groups. As a first step 1 went care- 

 fully through the whole of my collection and determined the sex 

 of every specimen. This was a matter of some difficulty, as 

 there are no prominent sexual characters in the group, and I soon 

 found that differences of colouration and in the form of the wings 

 were very deceptive and had led to many errors. A little exami- 

 nation however soon convinced me that the presence of anal valves 

 in the male, almost as well marked as in the genus P«pi/io, offered 

 a certain test of sex in Pieris and its allies, and as my collection 

 contains good series of many of the species from different localities, 

 I was soon led to satisfactory results in many cases. At the same 

 time T made tlie important observation that an extensive series of 

 species, evidently all closely allied, were characterized by large 

 tufts of stiff hairs or bristles springing from the base of each anal 

 valve and often extending beyond their extremity. Both African 

 and American species closely allied in form and colouration had 

 the same character, which moreover was not found to exist in 

 any other group of Pieridce. The character is not one wliich 

 Jias been hitherto used in characterizing genera, but as its presence 

 is in every case easily ascertained and it groups together species 

 which are evidently closely allied, it is probably of physiological 

 importance ; and as it enables us to break up into natural divisions 

 a very unwieldy mass of species, I have determined to form the 

 group so characterized into a genus which I term Tachijris, as 

 they have most of them pointed wings and a very rapid flight. 

 Pieris j^ctnda, Godt., and Pieris nero, Fab., may be considered the 

 types. 



I'he genus Thyca, established by Wallengren for the species of 

 Pieris which have only one precellular subcostal nervule (and 

 previously indicated as a section by Doubkday), is not adopted by 

 Vollenhoven in liis Monograph of Malayan Pieridce, because he 

 thinks it conflicts too much with other affinities. A careful exa- 

 mination of all the specimens having this character has led me to 

 the opposite conclusion, since the fifty-seven species I place in the 



