14 



THE AUSTRALIAN MUSEUM MAGAZINE. 



II— THE WHITE BUTTERFLY MIGRATION 



The White Caper Butterfly, 

 Anaphaeis Java var. tentonia, which, 

 during November, 1920, passed over 

 Sydney in swarms, has given rise to 

 much, speculation as to its ultimate 

 goal and the reason for its migration. 

 This butterfly is a member of the 

 family Pieridae. a group which in- 

 cludes those species popularly known 

 as "The Whites." Many species of 

 Pieridas are noted for their migratory 

 habits, and the great naturalist, Charles 

 Darwin, in his "Naturalist's V^oyage 

 Round the World," records a flight of 

 white butterflies which was seen from 

 the deck of the "Beagle" when ten 

 miles out at sea off the South Ameri- 

 can coast. In view of a theory put 

 forward at a recent meeting of the 

 I.innean Society of New South Wales, 

 that the migration of the "Caper 

 White" was probably due to the 

 westerly winds carrying them from 

 the West, it is of interest to read the 

 conclusion arrived at by Darwin when 

 he encountered the swarm of butter- 

 flies so far out at sea. "The day," 

 he says, "had been fine and calm, and 

 the one previous to it equally so with 

 light and variable airs. Hence we 

 cannot suppose that the insects were 

 blown oft" the land, but we must con- 

 clude they vohuitarily took flight." 

 Another theory as to the cause of the 

 migration was that the food plant of 

 the butterflies, the Australian Caper 

 Plant, had probably failed through 

 drought conditions and the insects 

 were forced to go further afield No 

 satisfactory conclusion has yet been 

 arrived at as to the motive for the 

 butterflies always travelling in a cer- 

 tain direction. The 1920 swarm is not 

 unique so far as New South Wales 

 is concerned ; we have records of 

 swarms in 1894, 1903, 1906 and 1909. 



During a migration, the insects 

 often appear at irregular intervals. 

 They may be conspicuous every- 

 where on certain days, hovering round 

 the flowers of the garden or floating 

 airily over the lantana blossoms, but 

 suddenly they disappear, to be fol- 



lowed perhaps in a day or so by 

 another body, which may lingei a 

 little longer before passing away on 

 its unknown quest. Weak fliers, they 

 make little headway against the buffet- 

 ings of adverse winds, and a white 

 flake on the green waters of the har- 

 bour too often bears testimony to an 

 untimely end from the forces of 

 nature. 



The "Caper White" has for many 

 years been known to frequent the 

 Native Caper plant, Capparis nobilis, 

 growing near the Herbarium in the 

 Botanic Gardens, and the butterfly 

 may be observed there in all stages 

 of its development. During the 

 recent migration, the butterflies 

 descended in hundreds on this plant 

 and were discovered laying their eggs 

 on the leaves to such an alarming 

 extent, that the tree had to be sprayed 

 several times with arsenate of lead in 

 order to dcstrov them. 



Two White Caper Butterflies. 

 (Male above and Female below). 



The spindle-shaped eggs of the 

 butterfly are laid on the upper side of 

 a leaf, sometimes as many as fifty 

 being deposited on a single leaf. The 



