PECULIARITIES OF FLIGHT 
535 
though not equal to the last-named, is a swift flyer, as are also many 
of the Teracoli , notably the South African T. eris. 1 
Commander J. J. Walker, R.N., writing of Euchloe belemia, Esp., 
at Gibraltar, Tangier, etc., said: “ It has a very strong, swift, and 
erratic flight, and is by no means easy to catch.” 2 Even the little 
Terias, which seems to go slowly, will be found to move so fast that 
a large proportion get away, though in this instance the mode of 
escape is commonly to dart downwards so that the net passes over 
the butterfly, and to the annoyance of the collector it rises again 
from the ground. There seems to me to be practically no doubt 
that the swift flight of the Whites and Yellows is due to their 
exceptional conspicuousness as compared with other butterflies. 
That they are exceptionally conspicuous is obvious enough. 
Yet not all Pierines are rapid flyers; there are marked and sig¬ 
nificant exceptions. Thus, many years ago, Dr. A. R. Wallace, 3 
writing of the Oriental genus Thyca {Delias), said: “ They have a 
very slow and weak mode of flight.” Again, at East London, Dr. 
Dixey called my attention to the “ slow, fearless, fluttering flight ” 
of Mylothris agathina, Cram. Both Delias and Mylothris furnish 
well-known models, closely mimicked by other Pierines. Dr. Dixey 
noted that the flight of the mimic Belenois thysa, Hopff., closely 
resembled that of its model Mylothris agathina, but Mr. E. E. Green 
tells me that Prioneris sita, Feld., a very close mimic of Delias 
eucharis, Cram., is a swift flyer. 
On March 30th, 1910, at Como, 12 miles S.S.W. of Sydney, New 
South Wales, I saw a number of males of Delias nigrina, Fabr., 
flying about the tops of Gum-trees {Eucalyptus sp.) that were in 
flower. They kept for the most part 30 or 40 feet from the ground, 
rarely coming down within reach. The upper side of the male is 
white with an apical black mark, the lower side mostly black. The 
effect of this strangely contrasted colouring was curious. The black 
and white surfaces showed alternately as it flew slowly about the 
flowers, and at first I took the butterfly for something much larger 
than it really was—to me it seemed a huge Papilio —I have seldom 
been so deceived in the size of an insect. The movement of the 
wings gave the butterflies a distinctly blue look, as might have been 
expected from the partial mingling of black and white. 
Probably belonging to a different category are two smaller Pierines 
1 See above, p. 222. 
2 Entom. Month. Mag., vol. xxiv., p. 181 (1886-1887); also Trans. Ent. Soc. Lond., 
1890, p. 869. 
3 Trans. Ent. Soc. Lond., Ser. 3, vol, iv., 1865-8, p. 309. 
