4 PARASITES OF THE COTTON BOLL WEEVIL. 



region in which the parasite- have reached the critical point of 

 maximum parasitism, and in such cases the overflow of parasites 



inuM attack some other host . which naturally will be the predominant 

 insect of the same group as their former host. It is therefore not 

 at all surprising that when the boll weevil appears by millions in a 

 new region these same parasites in the very first generation of the 

 boll weevil become adapted to it as a new host. 



The distribution of the other species of weevils is limited to floral 

 or geographical regions, and consequently, to a less extent, the para- 

 sites are also limited. Tins condition is illustrated by the distribu- 

 tion of the species of parasites which have already attacked the boll 

 weevil. It is safe to say that as the pest advances to the East and 

 North still other insects will adopt it as their host in the same meas- 

 ure as it invades regions inhabited by other species of weevils. In 

 many transitional regions there is a strong possibility that several 

 species of weevils may be very highly parasitized and that all of them 

 will lend parasites to the attack of the boll weevil. In such regions 

 especially there are to be expected instances of very high percentages 

 of parasitism. At Waco, Tex., where two regions border upon each 

 other, a parasitism of over 40 per cent occurred at one time during 

 the season of 1906. 



There are two possible practical applications of the information 

 obtained and recorded in this bulletin, both, however, requiring ex- 

 pert entomological knowledge and experience. These are: (1) The 

 propagation and collection of parasites, and their distribution in re- 

 gions where the same species are either present in but small numbers 

 or altogether absent, and (2) the elimination of related weevils by the 

 destruction of their food plants in or about cotton fields, thereby 

 forcing the parasites to transfer their attention to the boll weevil. 



Under the plan of artificial propagation by picking large numbers 

 of squares in fields where the weevil is highly parasitized and placing 

 them in cages adapted for such breeding, a large number of parasites 

 might be obtained. The weevils should then be killed. These para- 

 sites could be released in fields with a low percentage of parasit- 

 ism, and the results under favorable conditions should be apparent 

 after one generation of the boll weevil. In this bulletin will be found 

 an account of an apparently very successful experiment of this kind. 

 in which, at Dallas, Tex., the percentage of parasitism was brought 

 up 9.1 per cent by the introductions of parasites from Waco, about 

 100 miles away. 



Under the plan of eliminating, more or less, the natural hosts of 

 parasites that will attack the boll weevil (by the destruction of their 

 food plants) no experiment s have yet been performed. A- an exam- 

 ple of the possibilities, however, it may he mentioned that there i- a 

 common but easily controlled weed (Oroton spp.) grown in and about 



