23 



dering this forest there is another with exactly the same soil, the same 

 land of trees and of the same age as the other place, and although 

 these forests are separated only by a very broad road, in the latter wood 

 the caterpillars of almost all egg clusters of 1909 had emerged from 

 clusters that had been placed at any height on the trunks of the trees. 

 There were exceptional eases of clusters, sometimes on the upper, some- 

 times on the lower part of the trees, from which all caterpillars had not 

 emerged, but there was no evidence of the peculiar condition that 

 characterized the clusters in the place first mentioned. Whether any 

 caterpillar disease has any effect in this occurrence, I cannot now say. 

 The solution of this question may come in the future from careful ob- 

 servations at this particular locality.' 



An extensive forest in the southwestern part of Concord was visited, 

 in which, according to the information of the local superintendent, the 

 wilt had broken out naturally. The peculiar conditions which we found 

 here require a detailed description of the locality and of the manner 

 in which the disease operated. The largest part of the forest, about 

 20 acres, is situated upon the ridge of a hill. On the east and west 

 the hill slopes to wet meadows. On the north and south the hill gently 

 passes over into level country, and it is bordered here by broad roads. 

 The principal trees on the ridge of the hill are high pines about sixty 

 to eighty years of age; brush is almost absent. The slopes are covered 

 in large part with young oaks, which are much mixed with brush of 

 different kinds. Now, while the forest of the whole rid^e, including 

 the northern and southern slopes, suffered considerably from injuries 

 by gypsy moth caterpillars during the summer of 1910, the eastern and 

 western slopes were exempt from this damage. Soon after the cater- 

 pillars had passed the third molt Flacherie made its appearance among 

 those feeding on the pines upon the ridge of the hill. The disease 

 developed here so rapidly that probably all caterpillars were killed, for 

 we were unable, even by careful search in these 20 acres, on Sept. 7, 

 1910, to find a single fresh cluster. The statement, therefore, seems 

 justified that all caterpillars, at least all the females (100 per cent.), 

 were here killed by the wilt. This very high number, however, was 

 restricted to the forest upon the ridge of the hill. On the first trees 

 of the northern and southern slopes fresh egg clusters were found, and 

 the number of these increased as we went toward the plain. But the 

 inspection of such dead caterpillars as were observed showed that the 

 wilt had also operated in the woods of these slopes,_ The local super- 

 intendent looked here for Flacherie, but it did not appear till the cater- 

 pillars were in their last stage. The reason for this behavior of the 

 wilt might be that the ridge of the hill, with its high trees, was much 

 exposed to the effect of the wind, and after Flacherie had once devel- 

 oped it could be spread very rapidly along the ridge. On the northern 



' Similar observations, where eggs have not hatched, were made elsewhere by diSereat per- 

 sons connected with the moth work, but no definite observations, as at Concord, were reported. 



