SEASONAL FORMS 
577 
Plutella maculipennis, Curt. (orueifemrum , Zell.). 
England; Rannoch, 1868; Biskra, 1905; Hammam Meskutine, 
1905; Nerval's Point, Cape Colony, 1905; Gwaai, Mashonaland, 
1905; Egypt, 1909; New Zealand, 1910. 
§ 13. Seasonal Dimorphism. 
Seasonal Dimorphism has long been a subject of study in the 
Oriental and Ethiopian regions, but in the Neotropical world com¬ 
paratively little attention has been paid to it. 1 A visit of less than 
four months, and those within the limits of the winter, or dry season, 
affords but little opportunity for the investigation of such a difficult 
question-—and the difficulty is increased by the paucity of cabinet 
specimens bearing adequate data—nevertheless I venture to offer the 
results of my observations for what they may be worth. 
In the Old World we see in certain genera of the Satyrines that 
the same species exhibits two forms, characterized by the presence or 
absence of ocelli on the under surface of the hind-wings. Similarly 
two forms are met with in the Nymphaline genus Precis ; 2 in the 
one ocelli on the under side of the hind-wings are well developed, 
but in the other they are rudimentary or entirely absent. With the 
absence of ocelli is often associated a more angulated form of the 
wings, which are sometimes tailed, while the whole under surface is 
often of a redder colour, and the insect when at rest is cryptic, some¬ 
times resembling a dead leaf. Again, in many Pierines there are 
also two forms, the one characterized by the black markings on the 
upper surface being more pronounced, and sometimes by a suffusion 
or irroration of black scales; whereas in the other form there is an 
irroration of reddish scales on the under surface, with or without 
reddish or purplish markings. 3 Now these two forms have long been 
recognized as occurring for the most part in the wet and dry seasons 
respectively, though it must be admitted that in Terms and Oatopsilia , 
1 See Dixey, Proe. Ent. Soc. Lond., 1898, p. xxxix. 
2 Including Junonia. 
3 In Oatopsilia, Callidryas, and Ixias the disco-cellular spots on the under side 
of both fore- and hind-wings are usually larger, with larger white centres and alto¬ 
gether more conspicuous in the dry season. Moreover, in Ixias dry-season specimens 
have on the iunder side of the hind-wing a series of reddish, or purplish, post-discal 
spots, which when fully developed have white centres (especially in I. pyrene), and 
call to mind the similarly placed ocelli so well known in the wet- season forms of 
Mycalesis and Precis, and indeed they are not unlike the rudimentary ocelli seen in 
intermediate specimens of those genera, though they never attain to the complicated 
“ peacock-feather ” pattern so, pFft^cteyistfp of ni&ny Nymplutlidae. 
2 v 
