128 LOWER AMAZONS—PARA TO OBYDOS.  Cuap. VI. 
eastern parts of the Andes. Another butterfly nearly allied to these, 
Callithea Leprieurii, was also very abundant here, at the marshy head 
of the pool before mentioned. The wings are of a rich dark-blue 
colour, with a broad border of silvery-green. These two groups of 
Callithea and Catagramma are found only in tropical America, chiefly 
near the equator, and are certainly amongst the most beautiful pro- 
ductions of a region where the animals and plants seem to have been 
fashioned in nature’s choicest moulds. A great variety of other beauti- 
ful 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 butter- 
flies 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 pro- 
cessions were uninterrupted, 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 composed 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 has a very wide range, some being found from the central 
parts of the United States down to 32°S. lat., yet each distant region 
has its tolerably distinct local variety. But the effect of this general 
wandering habit of the group is, in the long run, a wide dissemination 
of the species ; the formation of local varieties, showing that the process 
is, nevertheless, a slow one. None of the species are found much 
beyond the tropics, but the genus is well represented within the tropical 
zone throughout the world ; and an East Indian kind (C. Alcmeone) is 
so nearly allied to a South American one (C. Statira), as to have been 
mistaken for it by some authors. 
A strange kind of wood-cricket is found in this neighbourhood : 
the males produce a very loud and not unmusical noise by rubbing 
together the overlapping edges of their wing-cases. ‘The notes are 
certainly the loudest and most extraordinary that I ever heard produced 
by an orthopterous insect. ‘The natives call it the Tananda, in allusion 
to its music, which is a sharp, resonant stridulation resembling the 
* 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. 
