ANIMALS FOR. 51 



deposits ova, which live in the mud ; and if a little 

 of this is taken and put into water, the C/iiro- 

 cephali will hatch in a few days. 



The Water-Flea (Daphnia pulex), and a number 

 of other small forms, belong to this family of 

 Crustacea. 



FIG. 10. 



The INSECTS constitute the largest family of 

 articulate animals. Whole tribes of many of the 

 orders into which they are divided live in the 

 water. No Aquavivarium can be considered per- 

 fect without some of the varied forms of aquatic 

 insects. Some are more common and easily caught 

 than others, and to these we will call attention. 

 We shall begin with the BEETLES (Coleoptera), as 

 they furnish us in this country with the most con- 

 spicuous forms of aquatic insects. The largest of 

 our insects is the great aquatic beetle called 

 Hydropliilus piceus. It is the type of the family 

 Hydrophilidce, which although species are found all 

 over the world, none are so large as in our own 

 country. This large beetle (Fig. 10) needs hardly 



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