452 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 2 



With healthy pupae 

 Dead but not parasitized 

 Parasitized 



Total 288 100 82 100 



In this comparison it will be noted that the percentage of dead 

 from other causes than parasitism remains almost exactly constant, 

 while that of parasitism is more than three fourths greater in New 

 Hampshire, or almost twice as large. It would have been better had 

 the number of cocoons from New Hampshire been larger, since it 

 would have lessened the chances for error, but the relative condition 

 of the promethea cocoons, similarly compared, as will be seen by the 

 following tends to substantiate the results with cecropia: 



With healthy pupae 

 Dead but not parasitized 

 Parasitized 



Total 662 100 308 100 



The number of cocoons thus classified falls a little short of the 997 

 which was mentioned as the total number studied, as there were a few 

 of somewhat doubtful origin. The greater proportionate destruc- 

 tion by parasites in New Hampshire is quite as strikingly brought out 

 in this comparison as in the other, and it is worthy of note that the 

 parasitism of promethea was uniformly higher than of cecropia under 

 all conditions, and the death through causes other than parasitism 

 lower. 



An attempt was made to determine whether the percentage was 

 uniformly higher or lower than the average in restricted regions, as, for 

 example, in the lower Merrimac Valley or along the "North Shore" 

 in Massachusetts. The results were all negative, and instead of sup- 

 porting the proposition tended strongly to indicate that immediate 

 local conditions had very much to do with the matter. Enormous 

 variations in parasitism were found in different lots from the same 

 town or from towns closely adjacent, and the only conclusions which 

 could be drawn from the considerable series of careful computations 

 which were made are that the average percentage of parasitism was 

 greater to the north than to the south, although there were frequent 

 exceptions to the rule. The futility of attempting to draw general 

 conclusions from a study of material from one locality seemed to be 

 well demonstrated, and it is likely that this will apply equally well to 

 other insects than those studied. 



