INSECTS AND PLANTS 49 



the calyx, the wound is healed perfectly in a short time, 

 and a corky outgrowth appears above the general surface 

 plane. This prominence has been termed a 'wart.' The 

 healing is completed before the hatching of the egg takes 

 place, and thus both egg and larva partake of the benefit 

 of its production. Occasionally warts develop from feed- 

 ing punctures which were small, but the exact conditions 

 under which this takes place have not been determined. 

 Nevertheless, the presence of warts is the most certain 

 external indication of oviposition in squares. In a series 

 of observations they were found to follow oviposition in 

 eighty-four per cent, of the cases." 



An important factor in the development of all economic 

 insects is their capacity for rapid development. And an 

 interesting experiment has been carried out to test the 

 powers of the boll weevil in this direction. A hibernating 

 weevil, laying one hundred and thirty-nine eggs by 10th 

 June, would probably bring half that number, say seventy, 

 to maturity by 29th June. There are at least four genera- 

 tions in a season, and, allowing for the same rate of increase 

 in the succeeding generations, the second generation would 

 number about two thousand four hundred and fifty; the 

 third eighty-five thousand seven hundred and fifty; and 

 the last and final generation, three million one thousand 

 two hundred and fifty, or a total of three million eighty- 

 nine thousand five hundred and twenty individuals, as the 

 progeny of a single pair of weevils and their descendants 

 in one season. Put in other words, the progeny from one 

 fertile hibernated female might, in the course of four 

 generations, that is to say in a single season, number one 

 weevil for every square foot of area in a seventy-five acre 

 field. As over fifty per cent, of the weevils are destroyed 

 by natural conditions, it is doubtful if the actual increase 

 in one season, from a single pair, ever exceeds two millions. 

 Alarming figures in all conscience ! 



The Mexican cotton-boll weevil is a strong flier, therefore 



4 



