23 



to carry a larger number of spores of Endofhia parasitica 

 shortly after rain periods than at other times. It is a note- 

 worthy fact thai insects Nos. 63 to 68, all Leptostylus macula, 

 and all yielding positive results, were taken at West Chester 

 twelve days after a rain. 



The large numbers of spores carried by L. macula is no 

 doubt explained by the fact that many spores must necessarily 

 adhere to the body of this beetle while it is eating pustules 

 of the blight fungus. It would be expected that this beetle 

 would carry both pycnospores and ascospores, and such was the 

 case, although the latter were very rare. The other insects 

 also were carrying pycnospores almost exclusively. These 

 pycnospores we believe were obtained for the most part by 

 brushing them off during the normal movements of the insects 

 over diseased and healthy bark, in the same manner in which 

 the birds obtained the pycnospores (21). The reasons for this 

 belief may be summarized as follows: 



1. Ascospores are carried away by the wind upon being 

 expelled from the perithecia (2 and 20). 



2. Pycnospores are washed down the trunks of trees in 

 great numbers by the rains, even during the winter months, 

 while ascospores are not washed down (18). 



3. Viable pycnospores can be obtained in abundance from 

 healthy bark below lesions (51a). 



4. We do not believe that the pycnospores were obtained 

 directly from spore horns, because these become hard when dry 

 and spores are not easily brushed from them. This conclusion 

 is substantiated by the fact that only one of the nine insects 

 which had been permitted to run over spore horn material in 

 the in sectary yielded positive results. 



There is another possible source for some of the pycnospores 

 carried. It is known that pycnospores are washed into the 

 soil around the bases of infected trees, and these have been 

 found to remain viable for a period of two to thirteen days 

 of dry weather (19). It is quite likely that some of the insects, 

 especially the ants, may have obtained considerable numbers of 

 pycnospores from this source. 



