200 THE entomologist's record. 



such as there are, appear to be referable to the movements of the 

 Callidryads. Anderson records that, in south-western Africa, for two 

 consecutive days, such immense myriads of lemon-coloured butterflies 

 were encountered by him that the sound caused by their wings was 

 such as to resemble the distant murmuring of waves on the sea-shore. 

 They always passed in the direction that the wind blew, and as 

 numbers were constantly alighting on the flowers, their appearance at 

 such times was not unlike the " falling of leaves before a gentle 

 autumnal breeze." Kenrick states {Kntanu, xxxii., p. 288) that he came 

 across a swarm of a species of ( 'allidn/aft on the borders of the Transvaal 

 a few years ago. The insects formed a stream about a mile wide, and were 

 slowly moving on, those in the rear flying forward to the front, this move- 

 ment being continued. He says that the species of this genus are diffi- 

 cult to collect, owing to their speed ; it was almost impossible to follow 

 them, and the only way to get them was to find the flowers they 

 frequented and wait for them. Trimen notes {Trans. E)it. So<\ Land., 

 1870, p. 383) that Colonel Bowker witnessed, in March, 1869, an 

 immense flight of Callidri/as florclla, all steadily moving on eastward 

 across the Maluti mountains in Basutoland ; in this swarm both sexes 

 were represented, the $ s being easily recognised by being mostly 

 yellow instead of greenish-white. Describing this flight, Bowker says, 

 " During my trip to No-Man's-Land in March, 1869, I crossed the 

 Maluti mountains at two different points going and returning ; and 

 throughout the journey, whenever there was a gleam of sunshine 

 between the prevalent showers, the exodus of CalUdrnax jiordla and 

 rhadia continued in one uninterrupted stream. These butterflies were 

 to be seen in countless numbers, from the deepest and darkest valleys 

 through which the Orange River forced its way, up to the highest 

 peaks, 10,000 feet above the sea, and all were steadily moving on east- 

 ward. Sometimes one of them would stop and take a sip from a 

 tempting gladiolus, or even turn back a few yards for that purpose ; but 

 it would be only for a minute, and then oft" it would hurry again as if 

 fearful of being left behind by its comrades." Bowker further 

 mentioned that he had seen similar gatherings both in the Cape Colony 

 and in the Trans-Keian country. As regards these appearances in Trans- 

 Kei (Kafi'raria proper), Bowker noted in March, 1883, that ('. /lorella 

 suddenly appeared in thousands, but became rare by the end of April. 

 Barber, in 1881, observed an extraordinary abundance of this species in 

 Griqualand West. The larvfe were observed in thousands on ( 'assia 

 arachno'idcs, a very abundant plant there. They stripped it entirely of 

 leaves, and then devoured the young shoots, and even the bark of the 

 stems. In March or April the butterflies appeared in luyriads. The 

 case is instructive as indicating how the migration, in force, of 

 species of this genus, is most probably occasioned by their having, as 

 larvffi, exhausted the supply of their proper food-plant in a tract where 

 circumstances had favoured their excessive multiplication. Trimen 

 points out {loc. cit., p. 32) that when " both sexes are represented in 

 the swarms, it cannot be doubted that these multitudinous invasions 

 of fresh territory must considerably widen the area occupied by the 

 species, and it seems probable that the world-wide prevalence of the 

 Pierinae, and the immense range of such genera as < 'alliilri/as and 

 Colias have been largely aided by both the ordinary and extraordinary 

 travelling tendencies of these butterflies. It may be added that when 



