4 PARASITES OF THE COTTON BOLL WEEVIL. 
region in which the parasites have reached the critical point of 
maximum: parasitism, and in such cases the overflow of parasites 
must 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. This 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 experiments have yet been performed. As an exam- 
ple of the possibilities, however, it may be mentioned that there is a 
common but easily controlled weed (Croton spp.) grown in and about 
