856 



EXPEBXMENT STATION RECORD. 



[Vol. 38 



amount of cambium reached by the cyanic! and the extent to which other parts 

 of the plant are dependent on the injured cambium. 



The wide difCerences in results of treatment of plants with potassium cyanid 

 are believed to be due to slightly different manners of treatment in the different 

 cases. Less injury is to be expected when trees are treated in the dormant 

 state. 



ECONOMIC ZOOLOGY— ElilTOMOLOGY. 



Pood habits of the swallows, a family of valuable native birds, F. E. L. 

 Beal {U. S. Dept. Agr. Bui. 619 {1918), pp. 28, pis. 2).— This is a report of a 

 technical study of the food habits of 7 of the 13 species of swallows occurring 

 within the limits of the United States, namely, the purple martin {Progne 

 &ubis) ; cliff, or eaves, swallow (Petrochelidon lunifrons) ; barn swallow 

 (Hirundo erythrogastra) ; tree, or white-bellied, swallow {Iridoprocne bicolor) ; 

 violet-green swallow {Tachycineta thalassina) ; bank swallow (Riparia rip- 

 aria) ; and rough- winged swallow (Stelgidopteryx serripennis) . All the species 

 are more or less gregarious and these 7 are of such wide disti*ibution as to 

 render their food habits a subject of economic interest. 



Lists are given of the insects identified in the stomachs of the 7 species, 

 together with the following table showing the relative proportions of the most 

 important elements of food of the species: 



Relative prqportitons of the most important elements of the food of swaUoics. 



The crow and its relation to man, E. R. Kalmbach {V. S. Dept. Agr. Bui. 

 621 (1918), pp. 92, pis. 2, figs. 3). — This new treatise on the economic status of 

 the crow (E. S. R., 7, p. 840) discusses in detail the beneficial and harmiiu 

 food habits of the crow, gives a general account of its life history and geo- 

 graphic distribution, and shows how it may be controlled where necessary. 

 It is pointed out that while the misdeeds with which the crow has been con- 

 victed greatly outnumber its virtues these are not necessarily equal in impor- 

 tance. Much of its damage to crops and poultry can be prevented while its 

 services in the control of insect pests can ill be spared. As the capabilities of 

 the crow for both good and harm are great, it is believed that an extermina- 

 tion of the species would have ultimate consequences no less serious than 

 an overabundance. 



A list of the insects and other animals and plants specifically or generically 

 identified in the stomachs of 2,118 crows examined is included. 



Diagnosis of a new pycnonotine family of Passeriformes, H. C. Obeb- 

 HOLSEB {Jour. Wash. Acad. Sci., 7 (1917), No. 17, pp. 537-541). 



