COMMUNITIES IN RUNNING WATERS 



315 



ilies Blepharoceridae (Fig. 89a) and Psychodidac (Fig. 896) is found 

 a longitudinal row of sucking disks. Many of the may-fly nymphs have 

 organs of attachment in the form of thickened and spiny rims on the 

 tracheal gills, and an adhesive, disk-like thorax. The organs of attach- 

 ment are especially unique in fishes and tadpoles of mountain streams; 

 mouth, lower lip and ventral surface, and on fishes the fins also, may 

 be reconstructed into sucking apparatus. This may occur in very 



Fig. 91.— Tadpoles from mountain streams: left to right, Bufo penangensis 

 (Malay Peninsula); Rana larutensis (Malay Peninsula); Rana jerboa (Java). 

 After Flower, Laidlaw, and van Kampen. 



different taxonomic groups. The whole mouth of armored catfishes, 

 which are found in great numbers in South America (e.g., Lithogenes 

 villosus in the rapids of rivers in Guiana, or Placostomus, Fig. 90) , is 

 developed into a sucker, as is the ventral surface of the cyprinid, Gas- 

 tromyzon, in North Borneo. 17 Spines on the ventral surface are often 

 helpful additions. The tadpoles of tropical mountain rivers and brooks 

 which have similar adaptations also belong to different groups of 

 Salientia (Fig. 91) ; 18 - 19 ' 20 these animals cling so tightly that they can 

 be loosened only with great difficulty. 



Finally, an attachment by means of spun fibers also occasionally 



