233 



It does not preserve greeus, but the browns are preserved and the 

 markings are ^yell brought out. 



Mr. Marten said that hot alcohol is equally good for all but green 

 larvae, and that the boiling water is not a necessity. They have some 

 very tine specimens i^reserved in this way. 



Mr. Forbes read the following : 



A SUMMARY HISTORY OF THE CORN ROOT APHIS. 



By S. A. Forbes. 



The points of special interest in the history of the corn-root louse are 

 the time and place of oviposition, the stage and place of hibernation, 

 the relations of the root louse to the leaf louse of corn, the alternative 

 food plants of each, and the relations of the root lice to ants. The ac- 

 count here given is based upon observations and experiments made by 

 myself and my assistants at the office, beginning with the year 1882. 

 The facts concerning oviposition were ascertained by simple observation 

 of the oviparous female in the tield and in the laboratory. The method 

 of hibernation was ascertained by field observations late in fall and early 

 in spring. The statements made concerning food plants other than 

 corn depend in part upon collections of the corn-root louse made on 

 various plants (the identity of the species being verified in each case 

 by successful maintenance and propagation on corn), and in part by the 

 incidental transfer of corn lice to other vegetation in our breeding 

 cages. 



The relations of the root lice to ants have been made out by very 

 many and careful explorations of formicaries in the field, by watching the 

 operations of ants among the lice, by laboratory experiments with artifi- 

 cial formicaries, and by various indoor experiments with ants deprived 

 of lice, with lice deprived of ants, and the like. 



The connection between root and aerial forms has been studied by 

 means of field observations intended to trace the first origin of the 

 latter in summer and their fate in autumn ; and especially by oft-repeated 

 breeding experiments with corn inclosed under cloth covered frames. 

 In our latest experiments of this sort, the cloth inclosures were very 

 large, to prevent the possible introduction of the leaf louse by the 

 females' producing young upon the cloth where the corn leaves touched it. 

 The earth within these inclosures was thoroughly disinfected, and 

 planted to corn in the spring, and colonies of ants were started here 

 and kept continuously supplied with corn-root lice throughout the 

 season, the object being to ascertain whether the evolution of the aerial 

 louse would occur under these strict conditions. We have also re- 

 peatedly tried the direct transfer of root lice of various generations to 

 the corn leaf, inclosed in a way to preclude outside interference. 



The principal facts arrived at can be most conveniently given in the 

 form of a biographical narrative extending through the year. 



