323 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 1 



the inter-relationships between a given host and a given parasite, it 

 must be remembered that this relationship is intimately connected 

 with the status of all the host-insects or host-plants of the given host, 

 and with all the co-hosts of the given parasite, and all of the host- 

 plants or host-insects of these co-hosts. Thus in the boll weevil prob- 

 lem the weevil has only one food plant to be considered, but it has 

 twenty-three primary parasites, three of which are sometimes acciden- 

 tally supernumerary ; also seven predators, which attack the l)oll wee- 

 vil or its parasites. Two parasites are known to attack these preda- 

 tors. Forty-one weevils are known to serve as co-hosts of the primary 

 parasites, some of them- harboring three or four species. Twenty-one 

 parasites, unknown to the boll weevil, attack these co-host weevils. 

 Ninety species of plants are known to serve as hosts to the forty-one 

 co-host weevils. The relationships do not stop here, for we know 

 other weevil hosts of the co-parasites of the co-hosts, and also other 

 parasites to these weevils, and finally hyperparasites on some of these 

 parasites. 



6. Fungous and hacterial diseases. Although very little is known 

 of the diseases of insects, the fact remains that many are carried off 

 by this factor. 



III. General Factors of Control 



1. Climate. Above all other factors and holding a definite relation- 

 ship to each, stands climate. As an agency of mortality it displays 

 its powers in many different manners. Frosts, rains, droughts, sun- 

 shine, shade, floods, storms and winds may be fatal, under the proper 

 conditions. That these factors do not influence different species in 

 the same manner is well known. The boll weevil is easily killed by 

 the direct rays of the sun falling upon it, or upon the square contain- 

 ing it, when the air temperature is in the nineties. The parasites are 

 not so easily affected. A frost in November, 1907, killed fifty-five 

 per cent of the weevil stages, but had no apparent effect upon the 

 parasite stages present. The relative fecundity, length of oviposition 

 period, rapidity of development, rapidity in sequence of generations, 

 proportion of sexes, dissemination, and aestivation or hibernation are 

 directly controlled by climatic conditions, and more or less arbitrary 

 formula? may be worked out after much study to represent each rela- 

 tionship. At the same time every plant and animal species involved in 

 the given problem is directly controlled by the same conditions. 



2. Plant conditions. The condition of the host-plant may very 

 greatly influence the given problem. For instance, it frequently hap- 

 pens that the cotton plant fails to form a complete absciss layer be- 

 neath an injured square or boll, and this injured part therefore is al- 



