MISCELLANEOUS NOTES. «13 



JJo. XXV.— ON METHODS USED TO PRESERVE COLOUE IN 



RELAXING ENTOMOLOGICAL SPECIMENS. 



By Colonel J. G, Pilcheu, F.B.C.S. 



Like most of my fellow-workers in Entomology, my attention was early 



called to the invariably altered colour of nearly all the blue and green 



moths submitted to moisture in the relaxing-box ; no specimen wholly 



retained its primitive colour, but became more or less yellowed in the process 



of relaxing. 



The only exception to this rule v/ere the fresh specimens which it has 

 been my custom to put into a moist atmosphere until the rigor mortis had 

 passed, when they were entirely freed from all rigidity, and yielded therefore 

 more readily to the touch of the needle than if they had Veen pinned and 

 allowed to partially dry before they are mounted. In passing I would note 

 the very great help this method has afforded in dealing with all fresh forms, 

 but especially with the small muscular Noctuidas. In fresh specimens dis- 

 colorarion was not so frequent, though it occasionally did take place in fresh 

 specimens submitted to a moi^t atmosphere for only a few hours. 



The thought occurred to me in 1889 that the cause of discoloration was 

 in free ammonia, due to the decomposition which must be presumed to 

 begin in the killing-bottle, and is renewed with greater energy when many 

 dried specimens are put into the relaxing- box at one time. And even 

 before the alkali has tainted the atmosphere of the relaxing-box it would 

 have been conducted to all parts of the specimen by its nervures and their 

 branches, 



A volatile acid suggested itself as a fit antagonist to the ammonia, and 

 carbolic acid seemed specially suitable, but its vapour was apparently not 

 diffiusiye enough, nor did it neutralize the ammonia as produced. 



Glacial acetic acid was found to answer best. I placed a small capsule or 

 measure-glass of this acid in the relaxing-box — 60-90 drops as a charge — and 

 renewed it as it evaporated, and this method I have used for many years. 



The relaxing-box or vessel which appears to afford advantages above all 

 others is a glass cylinder, covered with a round disk of glass ground to fit accur- 

 ately. Into this cylinder is placed a tripod of glass, to hold the clock-glass 

 upon which the specimens are to rest. Distilled water to the depth of half an 

 inch is put into the cylinder. The latter is then placed over a Bunsen's 

 burner, with wire gauze over it, and the water allowed to boil for five minutes 

 or more. On allowing the vessel to cool, a partial vacuum is produced, and 

 the cover must be removed with care some hours afterwards, when the 

 specimens to be relaxed and the acetic acid are then inserted. 



The vessel cannot remain completely sterilized because of the frequent 

 movement of specimeias to and from it, but heat can be applied from time to 

 time, and it can be kept, as free as possible, from those spores which do ger- 

 minate with marvellous rapidity in the saturated atmosphere of the relaxing- 

 box. 



