312 
PIERIDAE 
development. In Ireland, chiefly in Donegal, yellow forms, 
known as ab. jlava, Kane, occasionally occur. 
As in other species of the Pieridae, gynandromorphism is 
extremely rare in P. napi. In July, 1926, Mr. H. W. Head 
succeeded in breeding probably .a unique specimen, both 
dimorphic and gynandromorphic, having the left side female, 
ab. citronea n. ab., and the right side typical white male. 
In 1925 he also bred a perfect gynandrous specimen of ab. 
citronea with the right side male and the left side female. 
Among over 50,000 specimens of P. napi bred by Mr. Head 
during the past twenty-five years (the ancestor being a pale 
yellow form from Donegal), the large number of yellow types 
obtained show every gradation of colouring from the palest 
lemon-yellow to deep, rich citrine-yellow and dusky oclireous- 
yellow. The markings are equally variable in depth of 
colouring and development. 
Genus PONTIA, Fabricius, 1807 
THE BATH WHITE 
Pontia daplidice (Linn., 1758). 
(Plate XXV, facing page 292) 
This beautiful butterfly is a very scarce migrant to the 
British Islands, but is a common species on the Continent. 
It was first recorded as British by Petiver over two hundred 
years ago. It has occurred from time to time in some numbers 
in certain seasons, but chiefly in the south-eastern counties. 
The greatest number ever captured in one year in this country 
was in 1872, when about three dozen examples were taken 
during August and September. As many as twenty were 
recorded from Kent, eight in Sussex, four in Hampshire, the 
remainder in Suffolk and Cambridgeshire. In the same year a 
general invasion of other migratory butterflies to our shores took 
place, when large numbers of Camberwell Beauties, and other 
rarities, made their appearance. But during the last thirty years 
or more, the Bath White has been extremely rare in this country. 
