MULTIPARASITISM 



323 



have been destroyed. Pierce (1910), in his paper on insect enemies 

 of weevils, enumerates a number of examples of multiparasitism 

 involving competition between two species of parasites ; the 

 surviving species is recorded where known, but whether it gained 

 the ascendancy by direct attack upon its competitor or by indirect 

 nutritional effects was apparently not determined. 



In other cases of multiparasitism a passive struggle for existence 

 results, and the death of one or other parasite supervenes upon 

 exhaustion of the food-supply by the survivor. As a rule those 

 parasites which attack a given host earlier reach the destructive 

 feeding stage first and are consequently survivors in the struggle. 

 Thus, Tothill (1922), in discussing the parasites of Hyphantria 

 cunea, mentions that one caterpillar which he dissected contained 

 twenty-two parasitic larvae belonging to four species, and it is 

 doubtful whether any would survive to complete their trans- 

 formations. Sometimes the larvae of the Ichneumon Campoplex 

 succumbs as the result of the presence of the Tachinid Ernestia, and 

 sometimes the opposite occurs. When another Tachinid, Therio7i, 

 enters into competition it stands little chance of survival, since it 

 is the latest to attain the destructive feeding stage. It will be 

 observed in the accompanying table that the incidence of the 

 different parasites affecting the Hyphantria is more or less in a 

 sequence which consequently reduces the possibilities of 

 multiparasitism to a considerable degree. 



Table XIX. Sequence of Parasites of Hyphantria in 1913 

 (after Tothill). 



