302 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1951 



species sometimes causes trouble by crawling into the urethra of 

 bathers. The curious four-eyed fishes have the eyes divided into an 

 upper and a lower half for simultaneous vision in the air and under 

 water. There are two small fresh-water flyingfishes, not related to the 

 marine flyingfishes, and in the rivers formidable sting rays. 



The insects and other invertebrates are as diversified as the verte- 

 brates. Bather more than a third of all known butterflies, including 

 many endemic groups, are tropical American. Among these an 

 extraordinarily large number are vividly colored, the most spectacular 

 being the great metallic blue morphos; but the largest morphos are 

 dull in color. Then there are the huge owl butterflies {Cdligo) and 

 the noisy whip-crackers {Eamadryas or Ageronia). In the southern 

 Andes there is a satyrid or wood nymph almost wholly metallic silver 

 on both surfaces, and a skipper brilliant gold on the under side. 

 Among other invertebrates the giant bird-catching spider 8 inches 

 across should be mentioned, together with the giant wasps (Pepsis) 

 that feed on it and its relatives. The curious onychophores are 

 especially numerous in Central and South America. Those in the 

 Tropics belong to a group elsewhere represented only in tropical 

 Africa, while those in southern South America are related to others in 

 New Zealand and Australia. 



There are many other interesting features connected with the fauna 

 of the Americas — its origin, diversification at different periods in the 

 past and in response to present conditions, and the fundamental 

 changes that have come about since the settlement by Europeans, and 

 are continuing today with increasing speed. This brief survey, how- 

 ever, will suffice to bring out the similarities to, and contrasts with, 

 the corresponding faunas of Eurasia and Africa. 



