338 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



fomiity in the extent of parasitism in collections made in the older in- 

 festations near the District of Columbia and those more recent and 

 farther removed from the Potomac river. 



Macrocentrus sp. has been at all times the most abundant parasite 

 taken. In 1920, 132, or 92 per cent of the 143 specimens reared, were 

 of this spe,:ies. Apparently, it is becoming equally brooded with the 

 peach moth, specimens emerging from the first brood between the dates 

 June 24 and July 8, from the second brood between the dates July 24 

 and August 7 and fr^m the third brood between the dates August 22, 

 and September 21. 



According to Rohwer^ "the various species of Macrocentrus are in- 

 ternal parasites of mi^rolepidoptera, and the overwintering habit will 

 depend on the habits of the host. In most cases, they will overwinte*- 

 in their cocoons as prepupal larvae." 



Under normal conditions, the wintering, cocooned larvae of the peach 

 moth include small numbers of the third brood, and the fourth brood 

 in its entirety. A high degree of parasitism of the third brood affects 

 indirectly, therefore, the number of wintering lan^ae and the size of 

 the spring brood of moths, upon which the severity of twig infestation 

 is subsequently dependent. However, up to the present time, no par- 

 asites of overwintering larvae have been reared, and it seems certain 

 that Macrocentrus, and the other parasites as well, have failed to es- 

 tablish themselves as yet in this section of the seasonal life history of 

 the peach moth, and that they still continue overwintering on their 

 native hosts. It may be that this lack of parasitism of the fourth 

 brood is due to its distinctly fruit-feeding habit, as compared with 

 other broods, which may render oviposition by the parasites more dif- 

 ficult. Whatever the cause assigned, this fact, coupled with the low 

 mortality of the insect fjr the dormant season (about 85 percent of 

 the cocooned larvae have been found to overwinter successfully) ac- 

 counts probably for its greater abundance in the orchard and the in- 

 creasing destructiveness noted during the summer of 1920. 



Laboratory Tests With Nicotine 



Preliminary laboratory tests, involving 2877 eggs of the oriental peach 

 moth, were conducted by the writer in 1919 to determine the ovicidal 

 value of nicotine sulphate in respect to this species. The results were 

 promising, and have been reported.* 



^Correspondence. 



•'Jour. Eco. Ent., Vol. 13, No. 4, August, 1920, pp. 364-367. 



