195 



occurs, asexual reproduction proceeds without interruption. The 

 summer conditions in Texas are more adverse to Aphids than wanter 

 ones. During the long, hot and dry summers, green succulent vegeta- 

 tion is found only in low, damp and sheltered places. Migration of 

 T. graminum from grain occurs during June and July, when the grain 

 is ripening. A. pseudohrassicae was reared with difficulty throughout 

 the summer on turnips, when none were to be found in the field. 

 A. gossypii feeds entirely on cotton and okra during the summer months, 

 these host-plants being the only ones available at that time. In the 

 case of A. pseudohrassicae, during the hot, dry weather there is a 

 decided decrease in reproduction, all stages of the life-history being 

 lengthened in much the same way as under winter conditions. The 

 same observations have been made regarding A. gossypii in cage 

 rearing experiments. 



In the case of Pemphigus betae, Doan, (beet louse) there is a complete 

 reversal of the life-history. The alate viviparous females of this 

 species may be found on the foliage of turnips during October. The 

 apterous females feed on the roots of this host throughout the winter, 

 sometimes causing an appreciable loss in the crop. Alate forms are 

 found on the foliage again in March and later on Cottonwood. On 

 this host, the summer is passed in galls on the leaves. No eggs of 

 this species have yet been observed. 



The economic problems resulting from the presence of Aphids in 

 Texas have as yet received but little attention, and a great amount 

 of work remains to be done, especially in connection with the alternative 

 host-plants. 



Hartzell (F. Z.). a Method of Graphically Illustrating the Distribu- 

 tion of Injury by an Insect Pest.— J/. Econ. Entom., Concord, N.H., 

 xi, no. 1. February 1918, pp. 32-39, 2 figs. 



In studying infestations of insect pests, it is frequently necessary 

 for the entomologist to determine and describe the relations of the 

 insect to its environmental complex. As a means of conveying this 

 information clearly and accurately, graphs are found to be a method 

 of representation far superior to tables or written descriptions. Plans 

 for the preparation of graphs and maps and cardboard models are 

 described in this paper, and an example is given to illustrate the prac- 

 tical application of these methods. 



There are many advantages in the use of orthographic projection. 

 The amount of injury and its location throughout the area studied 

 can be clearly shown. The data can be presented with the finest 

 possible degree of accuracy. The charts assist in making proper 

 deductions regarding the relationships between the distribution of 

 the injury and the environmental factors. Data taken accurately 

 for the chart can be used for detailed biometrical analysis. Correlation 

 coefficients and equations will give relationships in a quantitative form 

 and can often be used as supplementary to an orthographic chart. 

 The chart can be made with comparatively little extra study of prin- 

 ciples and methods, and, if not too intricate, is readily comprehended. 

 Even an intricate chart presents the conditions throughout every 

 portion of the planting better than tables or any other form of 

 graphical or pictorial representation. A solid model of the conditions 



(C463) b2 



