46 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



Recent knowledge gives us no reason for assuming any density 

 dependent genetic factor that may operate in such a way as to control 

 and to maintain a proper "spread" of multiple parasitism with 

 reference to the resultant combined clutch size of the parasite and the 



Fig. 13. — Intensity of Clamator glandarius parasitism to Spreo bicolor indicated 

 by number of instances of each particular combination of egg numbers. 



host. Indeed, it is difficult to imagine just what such a factor or 

 factors might be. The available evidence, incomplete as it is, suggests 

 that it is not chiefly a matter of differential development of the habit 

 of host egg removal by the parasite that is responsible for the striking 

 difference we have found in the circum-Mediterranean and in the sub- 

 Saharan populations of Clamator glandarius. 



