October, '08] JOURNAL OF ECONOMIC ENTOMOLOGY 319 



itation is greatest in egg parasites, especially when the eggs are laid 

 separately, less so when they are in clusters. Parasites which attack 

 adults are not as a rule very numerous, although occasionally recorded. 

 The hymenopterous parasites of the boll weevil will attack either 

 larva or pupa, although Bracon mellitor generally attacks the younger 

 larvae. By this habit, this species frequently loses some of its value 

 through accidental secondary parasitism by other species. 



8. Dissemination. A migratory host species may frequently remove 

 itself many miles from its hereditary enemies by rising in flight. 

 The boll weevils disperse in all directions in the fall of each year, 

 being capable of moving fifty to a hundred or more miles. It is not 

 probable that the parasites can do this, because at present they are 

 known to be more or less limited in their distribution. Some of these 

 parasites certainly can not keep up with such a spread. On the other 

 hand, a migratory host may carry its parasites, as Toxoptera gra- 

 minum Rond. spreads its parasite Lysiphlehus tritici Ashm.^ 



9. Adaptation to new climates. In the event of a dispersion by 

 either host or parasite, or of an accidental or intentional introduction 

 of either species, it is of course necessary to understand the ability 

 of the species to accommodate itself to the new conditions of weather 

 and perhaps even of food. Although it is a very adaptable species, 

 the boll weevil frequently loses a good part of the territory gained 

 by the last dispersion of the year. 



10. Adaptability to changed food supply. When the food-plant of 

 a one-plant species, or the host of a one-host parasite, is checked by 

 any agency, a corresponding check is immediately placed upon that 

 insect also. Therefore, when either the host or parasite is thus re- 

 stricted and the other is capable of adjusting itself to other food- 

 supply, a decided advantage exists in favor of the adjustable species. 

 The boll weevil is al^solutely confined to one species of host-plant, but 

 its parasites without exception are able to propagate on several other 

 species of weevils. I have previously called attention to a sudden 

 adaptation of Ceramhycohiiis cushmani Cwfd., to the boll weevil, 

 because of the absence of its original host; of Eurytoma tylodermatis 

 Ashm., because of the cutting of weeds containing its host; and to 

 the rapid adaptation of Microdontomerus antJionomi Cwfd., which in 

 two years has become the predominant boll weevil parasite in certain 

 portions of central Texas. - 



•Webster, F. M., 1907. The spring grain-aphis, or so-called "green bug." 

 U. S. D. A., Bureau of Ent, Circular 93, p. 15. 



2The economic bearing of recent studies of the parasites of the cotton boll 

 weevil. Jour. Econ. Ent., Vol. 1, pp. 117-122. 



