1903.] E. P. Stebbing — Economic Enlomoloyy. 87 



stage, others in the egg or in the quiescent over- wintering stage. It 

 therefore becomes necessary to be able to recognise our pest in all its 

 stages of life. The matter becomes complicated, since when this has been 

 accomplished it may be found that there are several life-cycles in the 

 year and that the stages in one or more of them may differ from the 

 earlier or later ones. These variations reach their maximum in tropical 

 countries, where the number of life-cycles passed through in the year 

 may be as many as seven. Further complications arise owing to what is 

 known as alternation of generations, an insect living in one form, say, on 

 the stem or leaves of a plant at one period of its life and in quite a different 

 form on the roots at a later stage and season. We also saw that partheno- 

 genesis occurred when large numbers of females are born alive by a female 

 and in turn produce young ones, this state of affairs occurring through 

 the spring and summer months, a true sexual generation only appearing 1 

 in the autumn, this latter generation differing in appearance from the par- 

 thenogenetic females. This state of things compelled the conclusion that 

 we cannot rely upon the fact that life-histories and remedies worked out 

 and applicable in Europe or America will be of use to us or equally 

 justified in India. To do so will be to court disaster. The life-histories 

 of even cosmopolitan insects will vary in India and will be different in 

 different parts of the Continent. In introducing remedies the suscepti- 

 bilities of the Indian ryots must be taken into account and care be exer- 

 cised to introduce only such as will be possible to them and at the same 

 time within their means. 



We then considered the question of remedies and as to why their 

 study and introduction was necessary. It was pointed out that the large 

 increase of areas under cultivation and their greater increase which the 

 future held promise of, owing to the great irrigation projects now under 

 consideration, made the study of Economic Entomology an imperative 

 matter, it being an axiom that an increase in the area under any one 

 food plant meant an increase in the insect pests partial to it, since there 

 was so much food of easy access to them. 



In considering the subject of remedial measures we showed that they 

 divided themselves into two heads : (I) Those applicable through the 

 agency of man; and (2) natural checks brought into play by Nature her- 

 self. In the first group we touched briefly upon the question of using 

 spraying mixtures and the reason why some such, as, e.g., kerosine emul- 

 sion, were only applicable to insects with sucking mouths, since they were 

 required to clog up the breathing apparatus ; whilst others were designed 

 for use against biting insects, since they were of a poisonous nature and 

 were sprayed upon plants in order that they should be taken internally 

 with the parts of the plant consumed by the pest. 



