INDIRECT DEVELOPMENT 



339 



sea. But this larvae attaches itself to the gills of fishes and may 

 thus be carried up stream. 



723. Another type of larva is the trophic larva, like those of 

 many insects. These are characterized by their voracious 

 appetites. The caterpillar, for example, consumes much more 

 than is necessary for its daily needs. The excess is stored up 

 in the tissues as fat. When a certain stage of development is 

 reached, feeding ceases. The caterpillar finds a suitable place 



FIG. 211. Development of the frog. An example of indirect development 

 (metamorphosis). The gills have not disappeared in stage 6 but have been 

 covered by a fold of the skin. (From Galloway after Brehm.) 



in which to rest. Here a complete change takes place. The 

 skin is cast and there emerges a quiescent pupa, without func- 

 tional appendages, without mouth or eyes. In this form the 

 animal remains for a shorter or longer time, a few days to many 

 months. Then another radical change occurs. The pupa skin 

 is cast and the winged adult emerges. In many cases the adult 

 feeds very little. Some have no functional mouth parts and 

 would be unable to take food. They live for a short time, mate, 

 and deposit eggs. Here the adult is the dispersal stage. Its 

 organs of locomotion, the wings, are not for the ordinary pur- 



