October, '08] journal of economic entomology 32 1 



of this class may be given. Anthonomus sqiiamosus Lee. breeds in 

 the heads of GrindeJia squairosa, which heads are frequently entirely 

 riddled by a \avge noctuid caterpillar, Lygranfhoecia mortua Grote, 

 at the expense of the developing weevil. This same noctuid consumes 

 the larva* of Desmoris scapalis Lee. in the heads of Sideranthus 

 rubiginosiis, after the same manner. Lixus muscidus Say breeds in 

 stem galls of Polygonum pennsijlvwmcwm, but is frequently in the 

 path of a stem mining pyralid, which invariably consumes the weevil 

 stage or its parasites. Any such interference with the host insect, of 

 course, affects the welfare of its parasite species. 



3. Predatory insects. With certain striking exceptions predatory 

 insects do not show much discrimination between insects which might 

 become their prey. The most valuable of all predators are probably 

 the ants. In fact in the boll weevil problem they rank very high as 

 an element of control. Ants carry away every vestige of insect mat- 

 ter from the cell. They may devour larvae killed by heat or para- 

 sites. There is a question therefore as to the mortality to be accred- 

 ited to them, since some portion might have been accomplished by 

 heat or by parasites. The problem of utilizing ants is as complicated 

 as that of utilizing true parasites, because of the social economy of 

 these insects. 



4. Hyperpara^ites. The existence of hyperparasites is always very 

 provoking when the question of controlling an injurious insect is to 

 be solved. Before utilizing the primary parasites the worker must 

 attempt to eliminate the secondary parasites. The entire effective- 

 ness of a given parasite may be destroyed by its hyperparasites, and 

 again these may be almost completely checked by tertiary parasites, 

 and they by quaternary species. Still more provoking are the many 

 cases of species which act according to conditions as primary and 

 secondary, also even tertiary, or as secondary, tertiary, and quater- 

 nary, as shown by Howard, Fiske, Silvestri and others. Accidental 

 secondary parasitism, or that phase which is rendered so by the pri- 

 ority of another individual, occurs in the habits of Cerambyeobius, 

 Eurytoma, and Microdontomerus on the boll weevil. Frequently the 

 eggs of three species are found on a single weevil larva. Thus it 

 may he seen how the several co-parasites of an insect, although all 

 working to the same end may frequently work at cross purposes, by 

 each destroying some of the others. 



5. Co-Jiosfs. The sulijeet of co-hosts has received little attention 

 in the past. Not only do phytophagous insects frecpiently have many 

 host-plants, but it is also common for parasites to attack numerous 

 closely related species, or insects with similar haliits. In considering 



