METHODS OF COLLECTING INSECTS 



335 



searched for any nymphs or larvae that may be entangled in it. 



This form of net is particularly useful in collecting dragon-fly 

 nymphs, and is much superior to the ordinary 

 garden rake, which has often been recommended 

 for this purpose. 



Cyanide bottle (Figs. 472 and 473). These 

 bottles should be provided in at least three sizes, 

 the largest with a di- 

 ameter of two and one 

 half inches or more, 

 a smaller, straight- 

 necked bottle with a 

 diameter of an inch 

 and a half, and an- 

 other much smaller 

 straight-necked bot- 

 tle with a diameter 

 of about half an inch. 

 Before much collect- 

 ing is done, the stu- 

 dent will probably 



FIG. 472. A cya- find it necessary to 



nide bottle for the p rov ide himself with 



pocket. (One half 



actual size) 



two complete sets of 



these bottles, with 

 possibly one or two extra of the smaller 

 sizes. Cyanide bottles are made in 

 the following manner : Place a few 

 good-sized pieces of potassium cya- 

 nide (a most deadly poison) in the 

 bottom of each bottle, and cover the 

 cyanide with dry plaster of Paris. 

 (As the fumes of potassium cyanide 

 are very poisonous, it should be 

 handled with extreme care.) Then 

 mix up a thick paste of plaster of 

 Paris and water, and pour over the dry plaster in the bottles. 

 Leave standing open for a few hours, until the water has evaporated 



FIG. 473. A larger cyanide bottle 

 with paper strips to give sup- 

 port to the insects 



(After Banks) 



