APPENDIX 151 



the small red-legged locust (Melanoplus femur-ntbrum) 

 will be satisfactory. Some of these should be alive in the 

 laboratory for study of the habits of living specimens. 

 Preserve insects in alcohol, rather than formalin. 



Crayfish. Crayfish may be purchased alive from dealers, 

 or collected. If they are collected in the autumn and placed 

 in a tank (or tub) with water and kept in a cool, rather dark 

 place, they will live for a long time. If running water is 

 not available the water in the tank should be changed 

 occasionally, especially if a scum appears on it. 



For demonstrating water currents over the gills use 

 powdered carmine, India-ink, methylene blue, etc., and 

 drop along the edge of the carapace. A piece of the carapace 

 at the side of the mouth parts may be removed in the living 

 animal* if carefully done, and the movement of the gill 

 bailer demonstrated. 



The heart and larger bloodvessels are easily injected with 

 a thin starch mass. Either remove a piece of the carapace 

 and with syringe gently inject the mass into the heart, or 

 if the position of the heart is determined the carapace and 

 heart may be pierced with the cannula of the syringe. 



For preservation cut away a small piece of the carapace 

 on the dorsal side to permit the entrance of the preservative. 

 Alcohol is a better preservative than formalin since the acid 

 in the latter dissolves out some of the mineral matter of the 

 shell, and leaves an undesirable scum on the liquid and 

 about the animals. 



Clam. The fresh water clam is much easier and better 

 for study than the salt water forms. Use the larger forms. 

 If the valves are forced open and a wedge of wood, or a 

 pebble, is placed between to prevent closing, the animals 

 may be thrown directly into formalin for preservation. They 

 may be kept alive for some time in a cool place with running 

 water. 



