22 



Cluster 5. 



Unfertilized eggs, . . - \ Q7Q cent Qr about 6 5 per cent 



Eggs with dead embryos, . 5 j 



Eggs apparently alive, . . 69 =93.24 per cent., or about 93.5 per cent. 



Total, .... 74 eggs. 



Averaging these 5 clusters we have: 



Dead eggs, .... 20 =17.24 per cent., or about 17 per cent. 

 Eggs apparently alive, . . 96 =82.76 per cent., or about 83 per cent. 



Total, .... 116 eggs. 



A normal egg cluster contains on an average 433 eggs (p. 20) which 

 are apparently alive. Since the infested locality averages only 96 eggs 

 which are apparently alive per cluster, 4^/2 clusters are necessary to 

 equal the size of a normal cluster. The number of the fresh clusters, 

 estimated at 5,000, thus has to be reduced to about 1,100 clusters to 

 compare with the 10,000 clusters present in the spring of 1910. The 

 number of apparently vital eggs, therefore, is decreased to about 11 

 per cent, through the action of Flacherie. 



The local superintendent informed me that the disease had also spread 

 into the neighboring forest districts. By an extended walk through 

 about 5 acres of these woods I learned that the wilt had operated in 

 the same manner as in the first locality. He is of the opinion that 

 the number of clusters in this 5 acres has been decreased to about 

 15 per cent. Adjoining these woods there are about 15 acres of forest, 

 in which the local superintendent found that all egg clusters which 

 had been laid in the summer of 1909, and which had been deposited 

 1 foot or more above the ground, had failed to produce caterpillars, 

 that is, the eggs had remained unhatched; but the caterpillars had all 

 emerged from those eggs in clusters placed less than 1 foot above the 

 ground. I found that these statements corresponded very closely with 

 the facts. Here and there I noticed a slight exception by occasionally 

 finding either a high-placed cluster from which a few caterpillars had 

 emerged, or I detected close to the ground a cluster from which only 

 a portion of the caterpillars had emerged. These exceptions, however, 

 were insignificant, for they represented in each case hardly more than 

 10 eggs. I am unable, so far, to find any explanation for this peculiar 

 occurrence. At first I thought that an egg parasite might have exerted 

 its helpful power, but the examination of eggs from several clusters 

 which had remained unhatched showed that almost all eggs contained 

 a fully developed dead embryo, and no signs of a parasite could be 

 found. The moisture of the soil cannot be made responsible, for bor- 



