October, '08] journal of economic entomology 315 



and some of the trees were from one fourth to one half defoliated. No 

 spraying has been done this year, but the owners are ready to begin 

 whenever the occasion seems to warrant the outlay. The larvse ob- 

 served were mostly on the shoots in the center of the tree, and here 

 the leaves were badly eaten when those at the ends of the branches 

 were untouched. Several other orchards in New Haven County have 

 been examined for the sawfly and though traces of it have been found 

 nearly everywhere, in no case has it been so abundant as it was last 

 year in the Barnes orchard, and I doubt if any spraying will be done 

 to check it this year. 



I will here mention a point of considerable interest regarding this 

 species. Doctor MacGillivray described the insect as a new species, 

 but from the manner in which it appeared suddenly as a pest, some of 

 us felt that it might have been introduced. During April Mr. S. A. 

 Rohwer of Boulder, Col., wrote me for specimens, stating that he 

 was specializing on the sawflies. Specimens of both sexes were sent, 

 and these he acknowledged April 28th, and his letter contained the 

 following paragraph : 



"In a collection of sawflies which I am naming for the University 

 of Nebraska, I find two specimens of P. loersicum, taken June, 1903, 

 at West Point, Nebraska. This is rather surprising ! It seems to bear 

 out the idea that this pest is a native one." 



If the peach sawfly is a native species and occurs in Connecticut and 

 Nebraska, we should expect to find it in other states, and collectors 

 should be on the watch for it. After many observations have been 

 made we shall be better qualified to pass judgment regarding its 

 origin as a pest in this country. The distribution of this insect is 

 certainly an interesting subject. 



FACTORS CONTROLLING PARASITISM WITH SPECIAL 

 REFERENCE TO THE COTTON BOLL WEEVIL 



By W. DwiOHT Pierce, Bureau of Entomology. U. S. Dvpt. of Agriculture 



It is well understood that the relationships of parasites and hosts 

 are so intimate, and so delicately balanced, that any factor which 

 modifies in any manner the welfare of either species, at the same time 

 reacts on the other species. Consequently, in the case of economic 

 application of parasite control, the worker cannot afford to overlook 

 any aspect in the status or biology of either host oi- parasite, or of 



