PRESERVATIVE FLUIDS. 9 



tenure which have fallen off, inspissated ox-gall, softened with 

 a little water, is the best gum. 



For gumming insects upon cards, Mr. Wollaston recommends 

 a gum "composed of three parts of tragacanth to one of 

 Arabic, both in powder ; to be mixed in water containing a 

 grain of corrosive sublimate, without which it will not keep, 

 until of a consistency just thick enough to run. As this gum 

 is of an extremely absorbent nature, nearly a fortnight is re- 

 quired before it can be properly made. The best plan is to 

 keep adding a little water, and stirring it every few days, 

 until it is of the proper consistency. It is advisable to dis- 

 solve the grain of corrosive sublimate in the water which is 

 poured f:rst upon the gum." 



Preservative Fluids. The best for common use is alcohol, 

 diluted with a little water ; or whiskey, as alcohol of full 

 strength is too strong for caterpillars, etc., since it shrivels 

 them up. The spirits should afterwards be changed for alco- 

 hol of full strength for permanent preservation. Glycerine is 

 excellent for preserving the colors of caterpillars, though the 

 internal parts decay somewhat, and the specimen is apt to fall 

 to pieces on being roughly handled. 



Laboulbene recommends, for the preservation of insects in a 

 fresh state, plunging them in a preservative fluid consisting 

 of alcohol with an excess of arsenic acid in fragments, or the 

 common white arsenic of commerce. A pint and a half of 

 alcohol will take about fourteen grains (troy) of arsenic. The 

 living insect, put into this preparation, absorbs about y^o of 

 its own weight. When soaked in this liquor and dried, it will 

 be safe from the ravages of moths, Anthrenus or Dermestes. 

 This liquid will not change the colors of blue, green or red 

 beetles if dried after soaking from twelve to twenty-four hours. 

 Hemiptera and Orthoptera can be treated in the same way. 



A stay of a month in this arseniated alcohol mineralizes the 

 insect, so that it appears very hard, and, after drying, becomes 

 glazed with a white deposit which can, however, be washed off 

 with alcohol. In this state the specimens become too hard for 

 dissection and study, but will do for cabinet specimens designed 

 for permanent exhibition. 



Another preparation recommended by Laboulbene is alcohol 

 containing a variable quantity of corrosive sublimate, but the 

 s. M. c. 201. 2 



