335 



Group G. Sorae of the eggs of an eggmass are parasitized by 

 Trichogram ma and Phanurus, except a certain nurnber of healthy 

 eggs; these are called „T.'4-Ph. -f h." in the tables. 



Group 7. All eggs of an eggmass are healthy; these are named 

 "h." in the tables. 



The important object of this investigation is to learn, how raa- 

 ny of these eggs of Diatraea remain free from their parasitic ene- 

 mies. 



Therefore the 7 groups were reduced to 5 by the following rules, 

 in order to get a good diagram. 



a. Group 1. „T. all", 3. „Ph. all" and 5. „T. -\- Ph." are com- 

 {)Ietely checked as for the host eggmasses so that we have not to 

 correct the nurnber; just the same with group 7. 



b. Group 2. „T. half", 4. „Ph. half" and 0. „T. -f Ph. -f- h." are 



incompletely checked as for the host eggmass, therefore their nurnber 



is not effective and must be corrected, so that 



T. half -f Ph. half -f (T. -f- Ph. -f h.) , „ 

 ~ represents the real eiïective 



nurnber of destroyed eggmasses, forming one group in the graphic 

 representation. 



In the tables the material is separated in two kinds, viz. living 

 eggs and those which are already empty because the borers are 

 hatched or the parasites emerged out. 



The living eggmasses can be distinguished in parasitized and 

 healthy ones by the colour, but the healthy looking eggmasses are 

 not always surely healthy, because the parasitic eggs may be newly 

 laid in the fresh eggs of the host. In this case they are not distin- 

 guishable by the colour, unless four or live days have passed. 



Eggmasses of this kind were placed in a moist chamber, a glass 

 dish of 4 inches diameter with wet cotton, the eggmasses lying on 

 wet cotton linen on a glass plate until distinctly could be decided 

 between parasitic and really healthy eggmasses. 



A total nurnber of 5068 eggmasses investigated between the 

 HOtli of January and the 5th of March gave the following results, 

 as may be seen in the diagram of tig. 1. 



a. Eggmasses entirelyinfected with Trichogramma (,,T. all") 554 10,9% 



b. » » » » Phanurus („Ph.all")1621 31,9% 



c. » » » »Trich.andPhan.(\,T. + Ph")380 7,4% 

 cl. » only partly » » » » » 



or both, reckoned for one half 605 14,9% 



