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as a parasite of Japanese "beetle grubs. Owing to the fact that the acti- 
vities of this parasite are hidden under the soil and soil surveys are 
necessarily limited in scope, it is believed that the surveys are only an 
indication of the effectiveness of the species, .'The great abundance of 
males and females during the mating flights of this species certainly in- 
dicates a. greater degree of potential parasitized; ion than these few sur- 
veys indicate. The results of the surveys are shown in table 3» 
Table 3* — T. vernalis parasitization surveys 
: Yea.r : : Average : Total : 
Colora 1 - site (all : of : Area : grubs per: grubs : Parasitized 
in Pennsylvania) : survey: dug : sq. ft. ^recovered: grubs 
1/ : Sq, ft . : Humber : Humber : Humber : Percont 
Overbrook /Country Club . 1937 : 5^5 : 0.9 : 492 : 179 :: 36*^ 
RushlancF' : 1935: 200 : 5.7 : l,l46 : 702 : 61.3 
Do : 1936; 200 : 4.9 : S17 : 3SS.: 47.5 
Do : 1939; 200 : 5.3 : 1,054 : 506 : 4S.0 
Philmont Country Club -: 193*o : 200 : 5«7 : 1,142 : 66S : 5^.5 
17 
The Overbrook colony is considered to be within the older area 
of infestation, where beetle abundance has subsided, and we believe this 
has been largely due to grub parasitization by T. vernalis . In the year 
1936, prior to this survey, Tiphia was extremely abundant, 7 » 3^2 females 
being taken from this area. At the time of the survey the milky disease 
type A, incidence was 17 percent. 
2 / 
The Rushland colony is in a pasture approximately on the border of 
the area of moderate infestation. Only minor collections of Tiphia have 
been made at this point. The incidence of disease is unknown, but it is 
believed to be present. 
Interrela.tion of T. vernalis grub parasitization and milky disease . — 
The active period of parasitization by T. vernalis is from mid-May to about 
June 20, the Tiphia, thus attacking the larval population at its lowest 
point, after the high disea.se mortality of the previous summer and fall. 
If disease is present, its development during the spring period of Tiphia 
activity is so slow, owing to unfavorable soil temperatures, that it does 
not compete seriously with _T. vernalis . It is true that some overlapping 
does occur and that Tiphia will oviposit on diseased grubs but, if the 
disease is not in its' final stages, most of the parasites will complete 
their development, as they are immune to the effects of the organism. 
Other species of Tiphia which are active during the latter part of the 
summer and early fall, when soil temperatures are most favorable for dis- 
ease development, may be reduced in numbers b Tr the death of diseased 
parr.sitized hosts. 
Colonization of T. vernalis .— A total of 1,422 colonies. of this 
species have now been distributed in 9 Stales and the District of Colum- 
bia. Of these 150 were released in 1940. The Hew York (Geneva) and 
