Chap. YI. SWARMS OF BUTTERFLIES. 249 



of other beautiful and curious insects adorned these 

 pleasant woods. Others were seen only in the sunshine 

 in open places. As the waters retreated from the 

 beach, vast numbers of sulphur-yellow and orange 

 coloured butterflies congregated on the moist sand. 

 The greater portion of them belonged to the genus 

 Callidryas.* They assembled in densely packed masses, 

 sometimes two or three yards in circumference, their 

 wings all held in an upright position, so that the beach 

 looked as though variegated with beds of crocuses. 

 These Callidryades seem to be migratory insects, and 

 have large powers of dissemination. During the last two 

 days of our voyage the great numbers constantly passing 

 over the river attracted the attention of every one 

 on board. They all crossed in one direction, namely, 

 from north to south, and the processions were uninter- 

 rupted from an early hour in the morning until sunset. 

 All the individuals which resort to the margins of 

 sandy beaches are of the male sex. The females are 

 much more rare, and are seen only on the borders of 

 the forest, wandering from tree to tree, and depositing 

 their eggs on low mimosas which grow in the shade. The 

 migrating hordes, as far as I could ascertain, are com- 

 posed only of males, and on this account I believe their 

 wanderings do not extend very far. In confirmation of 

 this is the fact that, although the same species generally 



* More than three-fourths of the individuals in these congregations 

 of butterflies consisted of a pale sulphur- coloured species, C. Statira : 

 two yellow kinds, C. Eubule and C. Trite, and one orange-coloured, 

 C. Argante, were less numerous. A few of a much larger species (C. 

 Leachiana), sulphur- coloured with orange tips to the wings, now and 

 then occurred amidst the masses. 



