4 JNTR OD UCTION. 



vegetable-devouring insects. Many difficulties, however, stand in 

 the way of our determining which belong to one class and which 

 to the other, for paradoxical exceptions, which can only be likened 

 to the occurrence of herbivorous carnivora or carnivorous her- 

 bivora, or both at one and the same time, or at one time one 

 and at another the other, from time to time meet us, and there 

 are no means of saying ^/r/<?7V whether and when we are dealing 

 with such a case or not. Nothing but experience can enable us 

 to do so, and it is one of the objects of the collection to which 

 this is to serve as a Guide to assist those who desire it to acquire 

 that information. 



It may be proper to say a word or two in explanation of some 

 of the peculiar features of the collection and the reasons for their 

 adoption. The collection being destined for the instruction of 

 the people, it was of course desirable that it should be displayed 

 in such a manner as would be readily accessible and easily 

 examined, and upright cases open to view have been thought best 

 adapted for this purpose. The colours of insects are so evanescent 

 under exposure to the light, and the specimens themselves are 

 so fragile and subject to decay, that they are generally kept in 

 closed drawers or cases. The experience which the Museum 

 authorities have had with a case of silk-spinning moths, which are 

 so preserved in a locked case (accessible on application), has 

 shewn, however, that a collection so preserved would be practi- 

 cally sealed to the great majority of the visitors to the Museum. 

 They will not take the trouble to apply to see it. The collection 

 has therefore been made open to the public view, and the incon- 

 veniences thence arising are endeavoured to be removed by 

 occasional renewal of specimens and by giving along with each 

 insect a coloured representation of it, more or less magnified 

 according to the size of the insect — which, in the case of minute 

 insects, would be absolutely indispensable to allow their appear- 

 ance to be seen at all, and in larger ones has the advantage of 

 allowing the various parts to be more distinctly seen, and the 



