INSECTS AND MANKIND 421 



Arsenical sprays are used on a vast scale for the destruction 

 of the beetles, the operation of spraying being frequently 

 carried on from aeroplanes flying over the cotton fields, and 

 an indirect result of the Boll Weevil's activity is that the 

 price of arsenic has risen during the last ten years from 

 £19 to £62 a ton, and that a number of Cornish tin-mines 

 disused for years because tin ore no longer paid for raising, 

 have now been re-opened for the sake of the profits derivable 

 from the arsenical '' by-product." 



Though the Southern States of North America form still 

 the greatest cotton-growing district in the world, other 

 countries are coming into prominence as cotton-producing 

 centres ; among these Egypt, the Sudan, and Uganda are 

 now noteworthy. In Africa and Asia the most serious 

 cotton-pest is a caterpillar known as the '' Pink Boll- worm," 

 the larva of a small moth Pectinophora gossypiella. The 

 moth lays her eggs on the blossom and the caterpillar bores 

 in, feeding on the developing boll, and making its way into 

 the seed before pupation. According to H. M. Lefroy 

 (1923), 17 per cent, of the Egyptian cotton crop is destroyed 

 by this insect, and its ravages have cost that country about 

 £50,000,000 during the last fifteen years. The insect has 

 been introduced into the West Indies and Tropical America, 

 and the authorities of the United States are naturally eager 

 to prevent its establishment in their cotton belt. From the 

 summary of the life-cycle it will be realised that the wintering 

 larvae may be readily introduced in seed ; it is not surprising 

 that Egyptian cotton seed has been forbidden entry at 

 American ports, and that cargoes have on occasion been 

 destroyed. Such facts as these demonstrate the importance 

 now attached by the Governments of many great countries 

 to the control of insect pests. Nearly all national depart- 

 ments or ministries of agriculture have well-organised 

 entomological services the publications of which, with their 

 detailed accounts of the Hfe-histories and habits of injurious 

 insects, and instructions as to methods of killing the creatures 

 or preventing their ravages, prove that insects have forced 

 themselves on the serious attention of civilised mankind. 



