MIGRATION AND DISPERSAL OF INSECTS! LEPIDOPTERA. 237 
past, been established in the Bermudas. In 1864 it was taken 
in the islands of Fayal and Flores in the Azores, and in 1877, 
Grassal took it in France, at La Vendée. In the previous year, 
however, it had occurred in the British Islands, at Hayward’s 
Heath (Crallan), at New Close near Keymer (Wood), near Neath 
(Llewelyn), and in 1876 or 1877 an example was taken at Poole 
(Eaton) ; King has several specimens taken, in or about 1880, on board 
a vessel in mid-Atlantic on its voyage out, some 200 to 800 miles from 
the British shores whilst flying about the rigging of the ship. In 
1881 a specimen was captured at Snodland, in Kent (Hawes), and in 
1884, at Ventnor in the Isle of Wight (Westropp), whilst in the 
autumn of 1885 about a dozen specimens were recorded from Dorset 
(Cuttell), Devon (Hellins), Cornwall (Anderson, &c.), and the Isle of 
Wight (Billings). In 1886 more were captured in the south of 
England, at Swanage (Mowlem), Bournemouth (McRae), near the 
Lizard (Jenkin), in Pembrokeshire (Wilkinson), whilst others were 
reported from Guernsey (Luff), Gibraltar (Walker), and about 1890 a 
specimen was captured off the coast of Portugal some 60 miles from 
the Cape of St. Vincent (Harker). In 1890 another example was 
seen at Hastbourne (Clarke), and in June, 1896, a specimen was 
observed at Lymington (Waldo). The insect, however, has not yet 
made any permanent settlement in these islands, nor on the European 
continent. 
Tt would appear that in all those countries in which A. archippus has 
settled, its food-plant is some species of Asclepias, mainly Aselepias 
curassavica. The seeds of this plant are, Walker says, eminently fitted 
for dispersal, being very minute and enveloped in a great quantity of 
light cottony down, whilst the great hardiness of the butterfly, its 
almost complete exemption from the attacks of enemies, joined with 
its well known migratory propensities and habit of assembling in 
swarms render its chances of wide dispersal and ready adaptation to a 
new home especially favourable. Mathew states that he has often 
seen A. archippus “ flying at a great height above the ship, sometimes 
more then 200 miles from the nearest land. During a cruise between 
New Caledonia and the Solomon Islands, they were to be seen every 
day, often in numbers. They looked as if a steady migration was 
taking place, and the south-east trade wind, which was blowing 
strongly at the time, was greatly in favour of the butterflies accom- 
plishing their journey in safety.” Walker further adds that he has 
seen Danais chrysippus (misippus), a much smaller and less powerful 
insect than A. archippus, flying about the ship when she was 700 miles 
from the nearest land (the African coast) still strong on the wing and 
apparently in good order. 
Walker concludes that it is not difficult to imagine one of the great 
migrating swarms of A. archippus being blown out to sea from the 
Californian or Mexican coast, and travelling with the north-east trade 
wind, the greater number by far perishing en route, but a few stragglers 
of the host reaching the Sandwich Islands. This may have occurred 
many times before the introduction of a suitable food-plant, the 
butterfly necessarily failing to establish itself, but once the Asclepias 
was introduced it would soon be quite at home. Thence it would 
have no such tremendous expanse of ocean to traverse in order to 
reach new lands, the scattered islands between the Sandwich group 
