TO PRESERVE COLOUR IN RELAXING SPECIMENS. 39 



towards the costa ; the median segment is hollowed at the base below 

 the curved keel and, in the centre of this part are three not very 

 distinct, short, stout longitudinal keels. 



This species was reared from an acorn collected by Mr. E. P. 

 Stabbing from Quercus semicarpifolia in North-West Himalayas. 

 It agrees better with Callirhytis than with Andricus. One of 

 the European species of Callirhytis galls acorns. The Indian 

 oak-galls are quite unknown ; and there must be a splendid field 

 for any naturalist who would undertake their investigation. The 

 type of the species here described is in the British Museum. 



ON METHODS USED TO PRESERVE COLOUR IN 

 RELAXING ENTOMOLOGICAL SPECIMENS. 



By Colonel J. G. Pilcher, F.R.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 were 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 been 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 Noctuidse. 

 In fresh specimens discoloration was not so frequent, though it 

 occasionally did take place in fresh specimens submitted to a 

 moist atmosphere for only a few hours. 



The thought occurred to me in 1889 that the cause of dis- 

 coloration was 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 diffusive 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 — 



