FIELD BOOK OF PONDS AND STREAMS 



to cover; but some of them are easily stirred from their 

 hibernation and others are active all winter (PI. I). The 

 following list suggests a few of the things which can be found 

 in open spring-fed brooks or beneath pondice. 



In ponds and slow streams 

 October — November 



Salamanders ( Triturus) 



(P- 353) 

 Bullfrogs and green frogs 



(p. 385) 

 Water boatmen, backswim- 



mers (pp. 237, 239) 



CrayjEishes carrying their 



eggs (p. 172) 



Nymphs of dragonfiies and 



damselflies, abundant 



(p. 214) 

 Whirligig beetles (p. 271) 



In rapids 

 January — February 



Green alg£e (p. 49) 



Protozoans ( Vorticella) 



(p. 57) 

 Sponges (gemmules) (p, 104) 



Bryozoans (statoblasts) 



(P- 131) 

 Planarians (p. 119) 



Snails (p. 304) 



Mussels with young in their 



gill pouches (p. 318) 



Young insects, net-building 



caddis worms (p. 251) 



Care of living animals, life-history cages. — The way to learn 

 most about animals is to watch them in their own homes or 

 to keep them in cages which allow them to behave some- 

 thing like themselves. Such are the life-history cages within 

 which insect nymphs may be kept in their own brooks. The 

 simplest of these rearing cages (Fig. 33), one devised by 

 Dr. J. G. Needham, is made from a piece of wire window- 

 screening measuring about eighteen inches square. The 

 ends are brought together and hemmed over to form a 

 seven inch cylinder. The ends of this are then flattened 

 and hemmed and the cage is pillowed out to give comfortable 

 space within. One end can be easily opened when insects 

 are placed within the cage. In order to secure the different 

 stages of the life-history of water insects like dragonfiies or 

 mayflies, capture fully grown nymphs recognizable by their 

 black or very large wing-pads and put them in rearing cages 

 set a couple of inches down into the water of the insects' 

 home stream. Put only one kind of insect in at a time and 



36 



