239 



Mr. Riley said that experience showed that none of the generations 

 on hop would live on plum, except the winged female destined to mi- 

 grate to plum. He thought that we often can not do artificially what 

 nature does in her own time and in her own way. That sometimes a 

 species can not or will not colonize on another plant, to which it takes 

 readily at another season. He thought that many of the species have 

 an underground form during the summer, and that these forms in the 

 same genus resemble each other very closely, much more than do the 

 normal aerial types. Conclusions based upon comparisons merely are 

 often unreliable. Were the experiments on the root forms so made that 

 there was no danger of a mistake ? 



Mr. Forbes thought there was no chance of a mistake. They always 

 bred these root forms upon corn, and so brought the biological method to 

 bear, to supplement the systematic result.* Often in the fall, where the 

 root louse was on purslane, it would leave the roots and get upon the 

 stem, which they covered thickly. 



Mr. Riley said there was nothing more baffling than the study of 

 these insects. That from the same parthenogeuetic female may come 

 divergent forms resulting in either apterous parthenogeuetic individuals 

 like the immediate parent, or in winged or wingless sexuparse, and we 

 often fail where we try to treat them just alike. Species vary in color 

 and in characters, according to season or food plant, and comparisons and 

 descriptions that take no account of these changes are of little value. 



Mr. Forbes said the hypothesis that the apple and corn louse were 

 forms of one species was a very alluring one, owing to the fact that the 

 one seemed to disappear when the other arrived. The two species also 

 very closely resemble each other, except in the poriforous system of the 

 antenna. 



Mr. Riley said that the apple louse (mali) has a summer form on the 

 roots of grasses, and is found also on wheat in autumn. 



Mr. Forbes thought it would be through the leaf lice or aerial forms 

 that the apple and corn lice would be connected, if at all. 



Mr. Riley thought it would be more likely, from analogy, through the 

 root forms. 



Mr. Forbes presented a paper entitled : 



ON THE LIFE HISTORY OF THE WHITE GRUBS. 



By S. A. Forbes. 



Although there is a very great and steadily growing loss to the agri- 

 culture of this State (and doubtless in many others) due to the white 

 grubs or '^ grub worms," there is among both farmers and entomologists 

 a curious lack of self-consistent and trustworthy information concern- 

 ing their life histories. In fact, some studies of their transformations 

 begun by me in 1886 have led to the discovery that the biography 

 of these insects most generally current in entomological literature is 



