INSECTS AND PLANTS 51 



former, by directly reducing its vitality, resulting eventually 

 in death ; the latter, achieving the same result indirectly, 

 by interfering with the fruiting of the cotton plant and so 

 depriving the weevils of food ; but winter cold is, on the 

 average, twice as effective as summer heat. 



With regard to parasitic and predatory enemies of the 

 Mexican cotton-boll weevil in the United States, the Ameri- 

 can entomologists say that "it is known to be the host of 

 twenty-nine species of parasites, of which four are mites, 

 twenty-one belong to the order Hymenoptera, and five are 

 parasitic flies. In addition to these true parasites, there 

 are six predators which kill the adult boll weevils, and 

 twenty-two predators which attack the immature stages. 

 These include a mantis, a predatory bug, eight beetles, a 

 leaf-feeding caterpillar, and seventeen species of ants. In 

 all, the boll weevil is known to have fifty-eight species of 

 insect enemies, and probably many more species will be 

 found as the weevil enters new regions." A goodly host 

 of enemies, it must be admitted ; but the weevil apparently 

 thrives, despite them all. Space permits the mention of 

 one only of these weevil foes : the moth, Alabama argil- 

 lacea, known in America as the cotton-leaf worm. For 

 many years the larvae of this moth did an enormous amount 

 of damage among the American cotton-fields; in fact, in 

 some parts, it attracted almost as much attention as the 

 boll weevil does now. Changes in the cotton cultivation 

 and the use of an effective insecticide Paris green have 

 combined to reduce the damage done by this insect, and it 

 is one of the most extraordinary coincidences in the history 

 of economic entomology, that this formerly dreaded pest 

 is now regarded by farmers, in weevil-infested regions, as 

 decidedly beneficial. The cotton-leaf worms defoliate the 

 cotton plants, thereby checking their growth, with the result 

 that the opportunities for the breeding of the weevils are 

 lessened, and, as a consequence, their numbers are much 

 reduced at the end of the season. Again, after depriving 



