82 E. P. Stebbing — Economic Entomology. [Apr. 



requiring to be taken internally, against such insects since they feed 

 by suction, inserting their proboscis into the tissues of the plant. 

 A liquid, which merely coats the external surfaces, will not be taken 

 internally and will not therefore affect the insect. If, however, a liquid 

 of a thick soapy nature, e.g., such as kerosene emulsion, is sprayed upon 

 the plant it will thickly coat the leaves and stems and cover and clog up 

 the breathing openings of the suckiug insects feeding upon it and 

 suffocate and kill them. 



The second class of spraying solutions alluded to — the poisonous 

 ones — are for internal application. They are for use against insects with 

 biting mouth parts. These are often hard bodied externally and would 

 not be affected by the soapy liquids. In feeding upon the leaves, etc. 

 which have been sprayed over with the poisonous mixture they take 

 the poison internally and are got rid of. 



We shall refer to other remedial measures applicable by man later 

 on. The above two have been touched upon to show how the class of 

 remedy employed may depend entirely upon the structure and manner 

 of feeding of the insect. It will, however, be obvious that neither of the 

 two above mentioned remedies would be of the slightest use against a 

 pest which spends its life inside the stem of a plant or beneath the 

 bark of a tree, or the dangerous portion of its existence buried in 

 the ground feeding upon the roots. We shall cousider methods of 

 combating such attacks at greater length later on. 



We now come to the question of natural remedies or nature's 

 checks. These may consist of parasites, either insect or fungus. 

 Such checks follow nature's laws and pertain to her department, but 

 it may be shown that such can, when thoroughly understood by man, 

 be assisted and spread by his agency. 



It is probable that most insects are subject to these natural checks, 

 i.e., that most insects have at least one insect parasite preying upon 

 them and some may be subject to several. These natural checks are of 

 two kinds — the parasitic forms and the actively predaceous forms. 



The parasitic forms live as true parasites inside the bodies of their 

 hosts. Examples of such are the Ichnenmon flies, Chalcid flies, and 

 Tachnid flies — all exceedingly common and numerous in India. Impor- 

 tant as they are however to man, but little is at present known about 

 them in the country and our knowledge is not at present sufficient to 

 make any successful use of them. 



The predaceous group comprises those insects which actively prey 

 upon species of their class, feeding externally upon them, living in the 

 same haunts, and passing very similar lives. These are very commonly 

 mistaken for noxious pests by the uninitiated ; in fact, it may be said 



