22 PARASITES OF THE COTTON BOLL WEEVIL. 



1. Inasmuch as the parasites arc known to attack the weevil in 

 its first generation in a newly infested locality, it may he expected 

 that by releasing the proper parasites in a given locality the per- 

 centage of parasitism may he increased in a very short time. Such 

 a case was actually obtained by the release of Bracon meUitor at 

 Dallas, as described in the section on propagation. 



2. Dryness and sunlight assist attack by the chalcidoid and bra- 

 conid parasites of the weevil, as proved by the following considera- 

 tions: (It is, of course, to he understood that this conclusion may hold 

 only for those species and regions studied. In fact two or three of 

 the minor species, such as the tachinids, give promise of doing most 

 favorable work under directly opposite conditions in regions so far 

 unstudied.) 



a. Stages in hanging forms are, as a rule, parasitized to a higher 

 degree than those in fallen forms. 



b. Stages in fallen forms on prairie land are generally more highly 

 parasitized than those in wooded country, although frequently hang- 

 ing forms in wooded country are more highly parasitized than those 

 in prairie land. 



c. Fallen and hanging forms on unshaded ground are more highly 

 parasitized than those on shaded soil. 



These facts give an added importance to certain cultural methods 

 already advocated, viz : 



a. That the rows should be far apart, in order to allow the sun to 

 dry the squares on the ground. 



b. That determinate varieties should be planted in order to give 

 additional heat and light for the parasites during the cooler autumn 

 months. 



That, as indicated by the present studies, dryness seems to be a 

 most favorable condition for attack by hymenopterous parasite- is 

 quite natural, as these delicate little insects are very fond of sunlight 

 and warmth. 



II. Propagation Work. 



1. INTERIOR WORK TRANSFER OR ARTIFICIAL PROPAGATION OF 



PARASITES. 



It has not been a difficult matter to breed the parasites of the boll 

 weevil. There have been used in this laboratory four distinct 

 methods of obtaining parasites, all of which. served the purpose for 

 which they were used. In all cases where definite records of per- 

 centage, length of stages, or nature of parasitism were required 

 there has been a careful examination of each form (square or boll), 

 and those forms containing parasites, or sometimes only the para- 

 site and its host, were placed in individual pill bottles, numbered, 

 recorded, and placed in trays for daily observation. A somewhat 



