326 



it contains twice as much arsenic. Since calcium arsenate costs 

 rather less than lead arsenate and also has a higher coefficient of 

 adhesion, it stands far above all other materials for potato spraying. 

 The only contact insecticides used against leaf-hoppers were nicotine 

 compounds applied with and without soap, and only in the latter 

 case were they effective in destroying the insects. The present 

 mechanical methods of applying these materials are, however, 

 faulty, and future efforts should be directed towards improved 

 methods of application. 



Graham (S. A.). The Carpenter Ant as a Destroyer of Sound Wood. — 



17t}i Rept. Minnesota State Entomologist, Agric. Expt. Sta., Univ. 

 Farm, St. Paul, 1st December 1918, pp. 32-40, 8 figs. [Received 

 21st May 1919.] 



The carpenter ant, Camponotus pennsylvanicus, DeG., and its variety 

 ferrugineus, F., are well known to occur in decaying wood, but have not 

 been regarded as pests of sound trees or timber. It is now established, 

 however, that they are doing considerable damage to standing white 

 cedar in Minnesota, at least 20 per cent, of the trees cut showing 

 injury by ants to the stump. So far as observed, a perfectly sound tree 

 is never attacked, but entrance is gained through a wound or a decayed 

 spot usually near the ground, or even below the ground level. The 

 ants hollow out a nest in the heart of the tree, sometimes leaving only 

 a thin shell of wood round it, and thus seriously weaken the tree at 

 that point. From the nest they cut openings to the outside called 

 windows, from the presence of which a nest is easily located. The 

 height at which nests occur varies greatly, but they are usually within 

 6 feet of the ground. The percentage of ant-infested cedars varies 

 with the conditions under which the trees are growing, those in the 

 swamps being much less heavily infested than those growing on 

 higher ground. This may be due to the fact that the wet condition of 

 the ground tends to increase the moisture in the nests. The percentage 

 of trees with heart rot is also greater on the dry ground than in the 

 swamps and the wood of those grown in the latter situation is much 

 heavier and closer grained, and these factors may limit the extent of 

 infestation. 



No means of protecting cedar trees in the woods from ant attack 

 can be recommended at the present time, but intelligent trimming 

 of poles together with closer utilisation of ant-infested cedar would 

 result in the saving of an immense amount of merchantable timber. 



Oestlund (0. W.). Contribution to Knowledge of the Tribes and 

 Higher Groups of the Family Aphididae (Homoptera).— i///i Rept. 

 Minnesota State Entomologist, Aqric. Expl. Sta., Univ. Farm, St. 

 Paul, 1st December 1918, pp. 46-72. [Received 21st May 1919.] 



This systematic paper, which aims at bringing the arrangement 

 of the tribes and groups of the family Aphididae up to date, attempts 

 to give proportionate consideration to the historical, morphological 

 and biological aspects as necessary foundations of a natural classifi- 

 cation. Keys are given to the sub-families, groups and tribes. 



