STUDIES OF PARASITES OF THE COTTON 



BOLL WEEVIL. 



INTRODUCTION. 



Although the boll weevil (Anthonomus grand-is Boh.) has shown 

 adaptation to many diverse conditions, it is not free from parasites. 

 From the work detailed in this bulletin it has become apparent that 

 certain enemies attack it in arid regions and certain others in humid 

 regions; that some species attack principally larva? in dried or sun- 

 exposed forms, while other species attack the weevil stages in moist, 

 decaying forms; that some species work most readily in prairie 

 country, while others prefer woodland. The weevil does not escape 

 parasitism by dispersion, for the local parasites are -capable of 

 adaptation and attack the boll weevil in its first generation. 



Being a species with an all-season food plant, Anthonomus grandis 

 has made a decisive gain over most of its near relatives, which are 

 confined to more or less limited periods because of the shorter sea- 

 sons of their host plants. The most active weevil parasites in 

 the South have become adjusted to one host after another until in 

 most localities they have a regular seasonal rotation of hosts. From 

 this multiplicity of parasitic relations it is but natural to evolve a 

 new tendency and to attack the most abundant species of the locality, 

 namely, the boll weevil. 



As the native weevil hosts are more or less limited in distribution, 

 it is found that the boll-weevil parasites are likewise geographically 

 restricted. The combined activity of two or more species in certain 

 favored districts has been the cause of forming three known centers 

 of intensive parasitism in Texas, of which the most important is 

 near Waco; the next around Goliad, Cuero, and Victoria, and the 

 third in eastern Texas. The agencies forming these centers are in 

 no case identical. Catolaccus incertus is the most active parasite at 

 Brownsville, Tex., and Orange, La. Bracon mellitor (fig. 1), which is 

 the predominant parasite for the entire infested area, is the most 

 active in the entire western half of Texas. Oerambycobius cyaniceps 

 i> predominant in northeastern Texas. Eurytoma tylodermatis shows 

 its greatest activity at Overton and Dallas. 



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