88 NICARAGUA. 



transparent wings. ' Their elegant shape, showy colours, and 

 their slow way of flying, form quite a special feature of the 

 tropical forests. So also, the beautifully coloured Morphos, 

 the largest diurnal butterflies of America. The larger species 

 are about five inches wide, all of them brilliantly coloured 

 black and blue, sky blue all over, or opaline blue, so brilliant 

 that when lighted by the sun, their appearance is dazzling, 

 surpassing in beauty all other living animals. They have 

 also a slow way of flying, and they are as easily caught as the 

 Heliconi, but they are uncommon. 



One of the peculiarities attributed to the Heliconi is that 

 they are no food for birds. Why ? I have not been able to 

 ascertain ; but the fact remains that birds do not touch them, 

 contrary to their usual habit with all other species, of 

 w^hich they are very fond. The consequence is that other 

 butterflies, especially Papilios, are met with, resembling 

 so much to Heliconi in shape, colour, and other respects, that 

 it is supposed to serve them as a protection for life. 



Another interesting observation which I have made with 

 respect to the Heliconi is that various coloured varieties of 

 one and the same species are always met with typical 

 specimens. These may suddenly disappear and are replaced 

 by a large quantity of one of the varieties. 



Years after, this variety may disappear also and be replaced 

 by another variety. The deduction to be inferred from this 

 is that when a species is represented by a large quantity of 

 specimens. Nature produces the same changes that mankind 

 have done with several domesticated animals, such as 

 fowls, pigeons, dogs, horses, cattle, etc. 



Therefore it tends to prove that Nature is always at 

 work, and making continual changes in what we call species. 

 Some disappear and are replaced by new ones. It has 

 been always the same from the beginning of the world, 

 and will continue so to the end. 



Now-a-days we know with certainty that emigration or 

 transportation of animals and plants from one climate to 

 another, in the course of more or less time, will modify their 

 forms and their colours, for better or for worse, to such a 

 degree that they will be hardly recognisable. This is partly 

 due to the climate, and partly to change of food. 



On the 15th of December, I left San Juan, and with 

 several others, I started for la Virgen (the Virgin), the new 

 station built on the banks of the Lake of Nicaragua, where 

 small steamers w^ait for the passengers crossing the Isthmus. 



