316 JOURNAL OP ECONOMIC ENTOMOLOGY [Vol. 1 



any other insect, the biology of which may come in contact with that 

 of either species, directly or indirectly. 



A recent excellent review of the economic application of entomopha- 

 gous insects, by Marchal,^ contains remarks upon eight factors which 

 may influence or control the amount of parasitism by a given species 

 upon a given host. In studying this paper rather carefully I found 

 that several factors which are important in the boll weevil problem, 

 were not considered. With this in view the following notes, mainly 

 on weevil parasites, have been compiled. Twenty-four factors have 

 here been selected as distinct and of suiScient importance for indi- 

 vidual mention. These factors are grouped in three divisions. The 

 following were suggested hy Marchal : relative fecundity, hyper- 

 parasite.s, co-parasites, other plant-feeding insects, birds and other 

 vertebrate enemies of insects, climate, rapidity in sequence of genera- 

 tions, and retardation of development. Prof. C. W. Woodworth per- 

 sonally suggested the discussion of premature death, fungus diseases, 

 and duplicated mortality. All of the factors have probably received 

 more or less individual mention, but the grouping in this paper and 

 the illustrations are original. 



I. Biological Factors Involving Only Host and Parasite 



1. Relative feciindity of host aitd parasite. In attempting to util- 

 ize parasites or other entomophagous insects, the investigator should 

 always give the advantage of his efforts to the species surpassing, or 

 most nearly approaching the fecundity of the host. For it is very 

 evident that the species having the greatest number of offspring, all 

 other factors being equal, has the advantage. 



The relative fecundity is so important that it requires special atten- 

 tion before an extensive economic application is attempted. Not only 

 the total number of eggs laid by each species, but also the period of 

 oviposition should be ascertained if possible. Many species are able 

 to protract considerably the oviposition period, and thus a host might 

 easily gain the advantage over a one-generation parasite. It is not 

 sufficient to ascertain these points for onl}'^ a portion of the year, be- 

 cause of the varying length of the oviposition period and even of 

 fecundity, due to climatic influences. This may best be illustrated 

 by reference to the studies of Hunter and Hooker- on the cattle tick, 



i"The utilization of auxiliary eutoniophagons insects in the struggle against 

 insects injurious to agriculture." by Dr. Paul Marchal. Ann. Nat. Agr. Inst., 

 2d ser., vol. VI, part II, Paris, 1907, pp. 281-354; translated, Popular Science 

 Monthly, April, May, 1908, pp. 352-370, 406-419. 



2P>ureau of Entomology-. Bulletin 72. 



