386 - Dr. A. G. Butler—A Revision ~ 
twelve, expressing his firm conviction that all the other 
described forms were seasonal. So revolutionary a measure 
naturally met with considerable opposition at first, and is 
even now laughed to scorn by some lepidopterists ; but each 
collection received from the tropical parts of the Old World 
tends to prove that certain laws regulate the seasonal modifi- 
cation of Pierine butterflies and are never departed from. 
In the wet season Pierine are heavily marked with black 
spots, borders, and sometimes veins, often on both surfaces 
(though especially above) ; the under surface has a white or 
yellow ground-tint. In the dry season the under (and some- 
times the upper) surface shows much less black marking, and 
is frequently suffused with clay-colour, ochreous, or rose-red ; 
frequently, but especially when the ground-tint remains 
white, the apical area of the primaries and the whole surface 
of the secondaries are irrorated or finely striated with brown. 
’ The seasonal character of the above differences has been 
amply proved as regards the species of Teracolus, so that it 
is now possible to recognize a dry- or a wet-season form at 
sight ; nor is the fact that dated examples have been critically 
examined by any means the only evidence upon which con- 
clusions have been based, or even the unhesitating declarations 
of collectors in India and Africa, for in some cases the one 
form has been bred from eggs laid by the other, 7. auzo 
having been proved recently by Mr. Guy A. K. Marshall to 
be the wet-season form of 7. keiskamma, as supposed by 
Mr. Mansel Weale. 
Col. Charles Swinhoe objected to Capt. Watson’s decisions 
respecting the seasonal forms of certain Eastern Veracolz on 
the ground that he took them all flying simultaneously at 
Karachi—a fact which can be proved by an examination of 
the dates on the labels even of the Museum exainples. It 
must, however, be borne in mind that in countries where. 
practically no wet season exists great variation is often to be 
found, as pointed out by me in the case of Limnas chrysippus, 
Catopsilia florella, &c. (Proc. Zool. Soc. 1884, pp. 478-503), 
which there retain all the forms as simple sports of one variable 
species which in other parts of the Old World become fixed 
as local types. In like manner I find that phases answerable 
to dry-, intermediate, and wet-season forms exist in many 
species of Karachi and Arabia, and are simultaneously pro- 
duced. As an instance, Capt. Nurse bred Z. Yerburii and 
T. evagore from a series of exactly similar larvae, the perfect 
insects emerging at the same season. 
Again, lest it should be supposed that the yellow or ochra- 
ceous under-surface coloration was of specific importance, it 
