134 



SCIENCE 



[N. S. Vol. XLIII. No. 1100 



their conclusions the authors make the state- 

 ment (p. 28) that 



they (i. e., some insects) are important agents in 

 the local dissemination of this disease. This is 

 especially true of the beetle, Leptostylus macula. 



They also dispute the conclusion reached by 

 the writer^ that Leptostylus macula is a more 

 important factor in destroying the spores of 

 this disease, and state (p. 20) that 



the large number of spores carried by this beetle 

 certainly indicate that it may be an important 

 agent In the dissemination of the blight fungus. 



In the writer's opinion these statements lack 

 proof. From the fact that the insects have 

 spores on their bodies the conclusion can not 

 be drawn that they disseminate the disease. It 

 is shown that the spores may be brushed off 

 from the bodies of the insects even though 

 with difficulty, but the question is, Where are 

 they brushed off? If the life histories and 

 activities of many of these insects had been 

 more carefully observed an opposite conclusion 

 to that reached by the authors would appear 

 to have been a more natural one. To dis- 

 seminate this disease it would be necessary for 

 the insect to migrate from infested to healthy 

 trees. With most of the Coleoptera discussed 

 in this publication this is not the normal habit. 



In the case of Leptostylus macula it can be 

 positively stated that under normal conditions 

 this insect never frequents healthy trees. It 

 must be admitted that in crawling from one 

 canker to another for the purpose of eating 

 pustules, this insect possibly would spread the 

 spores to start a new infection on the same 

 tree, but this would be insignificant in con- 

 trast to the fact that the rain, as stated (p. 23), 

 washes these spores down the tree in large 

 numbers. 



The extent to which this, as well as certain 

 other species, feeds on these fruiting bodies is 

 illustrated by trees, examined by the writer, 

 on which from 50 to 75 per cent, of the canker- 

 ous area was eaten clean of pustules. From 

 such habits it would be natural to expect a far 

 greater percentage of spores on this species 

 than on others. 



2:SciENCE, N. S., XXXVI., p. 825, 1912. 



Of the three other species of beetles listed 

 by the authors as carrying spores, all are 

 known to feed on dead wood and therefore are 

 not likely to frequent living trees. Of the 

 thirteen ants collected under natural condi- 

 tions and tested for spores, only three were 

 found to carry those of Endothia parasitica. 

 Ants frequent living trees, especially those in- 

 fested by aphides, and in case they carry spores 

 conditions would be favorable for infection of 

 the wounds made by the aphides. But it is 

 shown that only a small number of ants in 

 nature were found to carry spores. Most of 

 the other insects discussed may be considered 

 as occasional visitors, such as those which rest 

 on the trees between flights; of these, few are 

 recorded as carrying spores. The only other 

 insects discussed that might possibly be re- 

 sponsible for direct transmission of the disease 

 are tree-hoppers, which might infect the 

 wounds they make while ovipositing. 



In discussing the dissemination of other 

 fungous and bacterial diseases by insects 

 (pages Y-11) the authors cite cases in which a 

 direct relation between host and insect can 

 be established, as fire blight of pear, spread 

 from blossom to blossom by pollen-bearing in- 

 sects, and by aphides which puncture the liv- 

 ing tissue; and ergot of rye, where the insects 

 are attracted by a saccharin solution oozing 

 from the conidia-bearing surface. In discuss- 

 ing the chestnut insects the authors establish 

 no such relation; in fact, the most important 

 insects, in the writer's estimation, in which 

 some such relation might be proven are not 

 mentioned in their experiments. The first of 

 these insects in importance is the longhorned 

 beetle Leptura nitens, which bores in the bark 

 of 90 to 95 per cent, of the living trees over 10 

 inches in diameter throughout the chestnut 

 range and in addition has adapted itself for 

 breeding in great numbers in chestnut blight 

 cankers. The interrelation thus established by 

 the beetle between the living, healthy trees and 

 the cankers on diseased and dead trees would 

 provide favorable conditions for the transmis- 

 sion of the disease. The adaptation of this 

 beetle to life in chestnut blight cankers has 

 become so marked in old infected tracts that it 



