( cxli ) 



its time or mode of flight, or its other characteristics, are in 

 any way different from those of an abundant species equally 

 suitable for food, it is not likely to be so much harassed as 

 these are. Creatures which are hunting for necessary food do 

 not spend their time, as " collectors" do, in quest of rarities. 



Fitness of the Imago stage for observation. 



I am well aware that most of my illustrations are taken 

 from the imago state, and that a far greater desti'uction of 

 life takes place in the earlier stages, and especially in that of 

 the larva. But in the last and most perfect stage of the life 

 of a lepidopterous insect a heavy toll is taken, sufficient in the 

 competition that exists to affect materially its power to hold 

 its own. Moreover it is the stage which admits of and is 

 usually associated with infinitely greater variations in facies 

 and habits than do any, — I think I may say all — of the others, 

 and it is that stage alone in which the senses and the nervous 

 matter which controls and directs habits have the widest scope 

 for effective action. It is therefore the stage in which the 

 materials exist in the greatest quantity for testing by actual 

 observation and experiment many of the questions that have 

 been discussed. 



Sivmrnary of propositions. 



Let me sum up briefly some of the propositions — I do not put 

 any of them forward as if they originated with me — which I 

 have submitted for your consideration. 



1. That in the life history of a species the number of its 

 offspring should be observed and recorded. 



2. That the consumption by herbivorous insects of their 

 food supply is not, except under special circiim stances, 

 a cause of the extinction or permanent reduction in 

 numbers of a species. 



3. That mutual competition is not usually of primary 

 importance in keeping down the numbers of a herbivorous 

 species of insect. 



4. That the chief factors in keeping down the numbers of 

 herbivorous insects are their active enemies. 



