REPORT OF EXECUTIVE COMMITTEE. 141 



(6) The correlation between the death rates at different periods of 

 life in man. 



(7) Certain minor problems in variation and correlation. 



A brief paper bearing the following title is submitted with the 

 report : "A table to be used in calculating the probable error of the 

 coefficient of variation." 



This table will be of practical utility in biometrical investigation. 



W. L. Tower, University of Chicago, Chicago, 111. Grant No. 181. 

 For an investigatioyi of the potato beetles of Mexico. $445- 



Abstract of Report. — This grant was made to aid in the continua- 

 tion of a research upon the evolution of the genus L,eptinotarsa, a 

 genus of beetle well calculated to give information concerning the 

 causes and methods of evolution in insects. The work planned to be 

 carried out under this grant falls under three heads : First, to trace 

 more accurately the distribution of certain species of these beetles 

 and to study the correlation of this distribution with topographic 

 and meteorological conditions ; second, to produce and transport to 

 Chicago certain species and their food plants for purposes of experi- 

 mentation ; third, to carry on observations in the Mexican tropics on 

 the life histories of these forms, and especially to study the factprs 

 most concerned in hibernation, and to start experiments in the 

 transplantation of species from one habitat to another. 



In order to carry out the investigation, Mr. Tower made two trips 

 to Mexico — one at the close of the dry season and one at the begin- 

 ning of the wet season. He determined important facts in relation 

 to the distribution and hibernation of the beetles, and records of 

 relative humidity, soil conditions, soil temperatures, air and sun 

 temperatures, in order to further continue the experimental work in 

 an intelligent manner. Living material of several species, together 

 with their food plants, were brought to Chicago successfully^ and 

 have thrived well under the conditions provided for them. With 

 this material experiments in breeding and hibernization and with 

 various environmental factors will be continued. 



Transplantations of various species were made from their native 

 habitats into habitats entirely new to them. These, if successful, 

 ought to give most valuable data concerning the effect of a new 

 environment in the production of modifications and new species. 



The results of this expedition consist in the obtaining of new and 

 needed material and of information concerning environmental condi- 

 tions during the rainy .season. 



