J2 SOME SOUTH INDIAN INSE< in. ETC. [CHAP. IX 



expect on the average to iiml at the end of the year? The answer 

 is very simple. As a rule, we shall find two individuals, only one 



of which will be a female, still capable of laying two hundred eggs 

 which will hatch and complete their lite-cycle in a month, hut whose 

 descendants will not on the average either increase or decrease in 

 numbers. 



What is the explanation of the enormous difference between the 

 potential and the actual rate of increase ? Briefly speaking, it may 

 be summed up under the three heads of (i) adverse climatic condi- 

 ' ) a limited food-supply and (3) the attacks of enemies, and 

 these causes may be further summarized under the general title of 

 i!i. Snuggle for Existence. On the one hand, then. Reproduction 

 and Growth constantly tend to the increase both of each individual 

 and of the number of individuals, and on the other hand the Struggle 

 for Existence tends to neutralize these forces, which togeth 

 stitute the Balance ol Lifeofthes] a -mule entity. On the 



whole, the balance remains fairly even and the numbers of any 

 specie's in a given area remain on the average approximately con- 

 stant in the absence of unusual environmental conditions, but the 

 beam of the balance is never at rest but is always vibrating slightly 

 on either side of its average position, and occasionally the be. mi 

 swings violently in one direction or the other as dearth or disease 

 or accident plays havoc with the numbers of the individuals or as 

 these increase with increase of food-supply or more favourable 

 en\ ironmental conditions. 



Every kind of insect or other living thing, therefore, is constantly 

 faced throughout its whole lite with the struggle for existem 

 has literally to succeed in the fight against competition and enemies 

 to be able to live at all. All animals and plants are constantly 

 engaged in this struggle and. whether their young or eggs or seeds 

 in. 1 , be counted on the fingers of one hand or be reckoned in millions, 

 on an average the number of any organism remains fairly constant 

 under unchanged environmental conditions. Man himself is not 

 exempt from the stress of competition, although his superior intellect, 

 in the more civilized races at least, helps him to defy many of the 

 natural checks on increase. In older and more uncivilized times it 

 was no uncommon thing thai 



" \ plague upon the people fell 

 A famine after laid them low, 

 Then thorpe and byre arose in fire, 

 1 them brake the sudden foe." 

 Even to-day in India it is not uncommon to hear of a village deci- 

 mated by a man-eating tiger or leopard whiKt even more 1 destructive 

 are the minute organisms, such as the malarial parasite- and the 



