RIVER MADEIRA 



209 



profoundest solitude reigned at the distance of a few 

 minutes' walk from the settlement. The first mile or 

 two of the forest road was very pleasant ; the path was 

 broad, shady, and clean ; the lower trees presented the 

 most beautiful and varied foliage imaginable, and a com- 

 pact border of fern-like selaginellas lined the road on 

 each side. The only birds I saw were ant- thrushes in 

 the denser thickets, and two species of Ceraeba, a group 

 allied to the creepers. These were feeding on the red 

 gummy seeds of Clusia trees, which were here very numer- 

 ous, their thick oval leaves, and large, white, wax-like 

 flowers making them very conspicuous objects in the 

 crowded woods. The only insect I will name amongst 

 the numbers of species which sported about these shady 

 places is the Papilio Ergeteles, and this for the purpose 

 of again showing how much may be learned by noting 

 the geographical relations of races and closely-allied 

 species. The Papilio Ergeteles is of a velvety black 

 colour, with two large spots of green and two belts of 

 crimson on its wings. Its range is limited to the North 

 side of the lower Amazons from Obydos to the Rio Negro ; 

 on the south side of the river it is replaced by a distinct 

 kind called the Papilio Echelus. The two might be con- 

 sidered, as they have been hitherto, perfectly distinct 

 species, had not an intermediate variety been found to 

 inhabit Cayenne, where neither extreme form occurs. 

 The two forms are as distinct as any two allied species 

 can well be, and they are different in both sexes. They 

 are found in no other part of America than the districts 

 mentioned. The intermediate varieties, however, link 

 the two together, so that they cannot be considered 

 otherwise than as modifications of one and the same 

 species ; one produced on the North, the other on the 

 South side of the Amazons. It is worthy of especial 

 mention that here as well as in the cases of P. Lysander 

 and the Heliconii, described in the preceding chapter, 

 the connecting links are found inhabiting distinct locali- 

 ties, and not mingled with the extreme forms which they 

 connect. 



We left Serpa on the 29th of December, in company 

 of an old planter named Senhor Joao Trinidade ; at 

 whose sitio, situated opposite the mouth of the Madeira, 

 Penna intended to spend a few days. Our course on the 

 29th and 30th lay through narrow channels between 



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