MIGRATION AND DISPEKSAL 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 Vendee. In the previous year, 

 however, it had occurred in the British Islands, at Hay ward's 

 Heath (Crallan), at New Close near Keymer (Wood), near Neath 

 (Llewelyn), and in 1876 or 1877 an example Avas taken at Poole 

 (Eaton) ; King has several specimens taken, in or about 1880, on board 

 a vessel in mid-x\tlantic on its voyage out, some 200 to 300 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 (Bilhngs). In 1886 more were captured in the south of 

 England, at Swanage (Mowlem), Bournemouth (McEae), 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 Eastbourne (Clarke), and in June, 1896, a specimen was 

 observed at Lymington (Waldo). The insect, how^ever, has not yet 

 made any permanent settlement in these islands, nor on the European 

 continent. 



It would appear that in all those countries in which A. archippus has 

 settled, its food-plant is some species of Asdcjnas, mainly Asclepias 

 cnrassavica. 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. archippm " 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, wdiich 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 chryaippus (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. 



W^ilker concludes that it is not difticult to imagine one of the great 

 migrating swarms of A. archijipus 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 



