CLASSIFICATION OF ANIMAL PREPARATIONS. 



419 



Curculionidse, require little or no preparation, and may be 

 mounted on discs and examined as opaque objects, whilst 

 others, such as the probosces and lancets of flies and bees, wiU 

 demand no small amount of skiU, in order to display them to 

 the best advantage ; when thin and transparent they should 

 be mounted in fluid, but in balsam when they are thick and 

 opaque. Previous to being mounted in the latter way, all 

 specimens of the probosces or lancets should be dissected 

 whilst soft, and then laid out in a proper position upon a slide 

 to dry; as those that are taken from recent insects and placed 

 in balsam immediately, generally make it appear milky. The 

 list given below will contain the names of some of those in 

 which the most important varieties wfll be found : — 



Parasitic Insects. — These, when caught, should be placed in 



spirit and water, in order to kill them ; those that are very 



transparent may be mounted in fluid, the glycerine or 



Goadby's solution will answer well ; some persons, however, 



prefer castor-oil, as recommended by Mr. Warington. If the 



specimens be very opaque, they may be dried and mounted in 



Canada balsam ; some of the large kinds, such as the various 



species of Ixodes, with peculiar instruments for adhering to the 



skin, may be mounted on discs and examined as opaque objects. 



The term Epizoa has been applied to this class of insects, in 



consequence of their being found on the exterior of animals, 



and in contradistinction to those occurring within, which are 



called Entozoa. The species of the former are exceedingly 



numerous, and but few hitherto have been described ; scarcely 



any animal of the higher classes is free from them during 



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