142 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



elevation, are exceedingly important when life-histories are being 

 dealt witb, and such should always be given. 



In addition, the following points should be borne in mind : — 



i. In the case of the greater number of our insects it is 

 absolutely necessary that the imago stage should be 

 obtained, otherwise identification is impossible. Beyond 

 being able to place larvpe sent by themselves into their 

 orders, groups, and perhaps families, no further identifi- 

 cation is possible, and thus sent alone they are of very 

 little use. 

 ii. In the furtherance of the study of Economic Eatomology, 

 it is of very little use sending insects " found flying 

 about" in the forest or in cultivated land unless some 

 further definite observations have been obtained about 

 them. Economic Entomology means the study of the 

 life-histories of insects with a view to endeavouring to 

 counteract the damage done by their attacks. Thus, in 

 the first instance it is necessary to know that an insect 

 is an aggressor and to be able to give the nature of its 

 attacks, or at any rate to state definitely that it does a 

 particular damage. 



As different insects require slightly different treatment, I will 

 now, in conclusion, give a few notes on the rearing of insects of 

 some of the more important orders. 



Collection and Preservation of Lepidoptera. 



A knowledge of the order Lepidoptera is of importance to the 

 forester, since it contains larvae which defoliate trees on a large 

 scale, and at the same time others which do serious damage by 

 boring into timber. When larvse are kept in order to enable the 

 subsequent stages in their life-histories to be ascertained, great 

 care should be taken to keep a supply of fresh food always in 

 the box in which they are enclosed. In changing to the pupal 

 stage, some larvee will spin a cocoon amongst the leaves of the 

 plant, or will attach it to the sides of the box. Others, on the 

 other hand, require earth to pupate in, and this earth should be 

 placed at the bottom of the box, failing which it is probable 

 that no imagoes will be obtained. Other larvfe may require chips 

 of wood, etc., to hide beneath; many Noctuid larvse, some of 

 which defoliate on a considerable scale, require this, as they often 



