10 INSECT ENEMIES OF THE BOLL WEEVIL. 



predators, and other pests remove many ants. Proliferated plant 

 tissue frequently acts as an important check upon the weevil, and yet 

 in many cases it serves as a food for the weevil rather than as a con- 

 trolling force. Moist weather aids the weevil. The leaf-worm, while 

 cutting off most of the weevil food, finally is checked by parasites. 

 Light, heat, and dryness favor certain parasites, whereas shade and 

 moisture favor others. Parasites that are normally primary fre- 

 quently waste their energies by accidentally becoming secondary, 

 and normally secondaiy parasites, and probably tertiary as well, also 

 enter the consideration. Predatory enemies fail to distinguish the 

 parasites from the weevils, but are in turn held in check by their own 

 enemies. The birds devour weevils, predators, and parasites, but 

 they in tiu-n are kept down by other bu'ds and even man himself, 

 and thus the complexity grows. 



There are 49 species of insects which attack the immature stages of 

 the boll weevil. Of these insects 29 species may be classed as para- 

 sitic, 5 as predatory larvae, and 15 as predatory adults. They are 

 divided among the orders, with 3 in the Acarina, 4 in Coleoptera, 36 

 in Hymenoptera, 5 in Diptera, and 1 in Lepidoptera. One of the 

 acarians, 1 coleopteron, 15 Hymenoptera, and 1 dipteron, may be 

 considered as quite important. A weighted average mortality of 

 3.93 per cent of all immature stages may be accredited to the com- 

 bined factors of all parasitic enemies; the predators are responsible 

 for 15.93 per cent, while climate is responsible for 24.45 per cent, and 

 plant proliferation 12.42 per cent. This makes the total natural 

 control of immature stages 56.73 per cent. 



In addition to the insects attacking the boll weevils in the squares, 

 there must be considered the insects which prey on the adults. These 

 include one praying mantis, one predaceous bug, two beetles, and 

 two ants — six species in all. 



This bulletin is not concerned with the mortality of the weevils 

 after they become adult because reliable figures can not be gathered 

 upon this point. It is certain that many weevils fall prey to preda- 

 ceous insects and to birds, and the well-kno^vn habits of the horned 

 lizard would include it in the list of possible enemies. The important 

 fact is that 56 per cent of the weevil eggs fail to produce adult weevils. 

 The remainder is still a formidable number but the many adverse 

 influences continue to operate upon the adults and likewise upon 

 their progeny. 



CONDUCT OF THE PARASITE PROJECT. 



The investigation of the insect enemies of the cotton boU weevil 

 was initiated in 1905. It has been conducted from the beginning by 

 the senior author under the direction of Mr. W. D. Hunter, and with 



