326 INTRODUCTION TO ZOOLOGY chap, xxi 



net-dipping in the mud at the river bottom will probably produce 

 some larvae. If large larvae are kept in a tank, it is indis- 

 pensable that facilities be given them to leave the water and 

 burrow in soil for their pupation. 



2. The Lacewing-fly of the garden is a far more satisfactory 

 subject for study, for its whole history can be traced in its natural 

 habitat, or, if more convenient, in a well-ventilated box in which 

 shoots infested with Aphides should be placed, so as to yield a 

 good supply of food. 



3. Caddises form a most interesting subject for study, and they are 

 quite easy to find and to keep through the different stages of their 

 development. They should be brought home from a pond in a 

 tin with only some water-weed in it ; they travel better thus than 

 in a jar of water. They need a carefully kept home ; any decaying 

 matter in the water soon affects them harmfully. They feed 

 chiefly on water-weed, but seem to relish occasionally a little piece 

 of raw meat. As soon as they have entered the pupal stage, means 

 of exit from the water must be provided, ready for the moment 

 when the pupa swims to the surface in order to enter the air before 

 it casts its skin and emerges as a winged creature. Interesting 

 observations can be made on the construction of new cases by the 

 caddis-worm when it is provided with a variety of materials from 

 which to choose. 



