38 
DANAIDAE 
now and again takes place in certain years and several 
individuals arrive on our southern coasts, as was the case 
in 1885, 1886 and again in 1933. It is quite possible that 
during their great flight across the Atlantic, these butterflies 
rest at times on the surface of the sea and rise again to continue 
their journey in the same way as other migratory species have 
been seen to do. 
Haunts and Distribution. On arrival in this country, 
D. plexippus has mostly been found frequenting gardens, 
being attracted by autumnal flowers. It is only endemic in 
the south of the United States and Central America, where 
a succession of broods occurs owing to the absence of cold 
weather. From this region it annually migrates northwards 
in the spring, when it spreads over - central and northern 
United States and far into Canada, where a continuity of 
broods is produced. The advent of cold weather exterminates 
them in these northern regions until a fresh arrival takes place 
the following spring. D. plexippus has no hibernating period. 
The migratory instinct of this great butterfly is so strongly 
developed, that during comparatively recent years it has 
wandered immense distances and has been met with at 
sea hundreds of miles from land. It has spread westwards 
over the Pacific to Australia and the Malay Archipelago, and 
eastwards to the Canary Islands, where it is now well estab¬ 
lished. But very few specimens have been recorded as 
occurring on the Continent of Europe. The first occurrence 
of this species in Europe was the one already alluded to, 
captured at Neath, Glamorgan, in 1876 ; the specimen is 
preserved in the British Museum (Natural History). 
D. plexippus , like all the other species of the genus, secretes 
a very disagreeable, nauseous odour, rendering it uneatable 
by birds. Those arriving on our shores and those seen at 
sea nearing land, have usually been slowly flapping along, 
but it has also a very powerful flight, flapping, soaring, and 
gliding with ease and grace. 
Egg Laying. This fine butterfly deposits its eggs singly on 
the upper surface of the leaves of different kinds of Milkweed 
( Asclepias ), and as no kind of Asclepias is indigenous in 
Britain, this insect can never become a resident in this country 
or even produce a single brood. Only on one occasion has this 
