12 THE AUDWEB OWN BU DIVE Piss 

time that they usually remain with us. Frequently Warblers that should 
have been well on their way by the third week of May remain with us 
until the first week of June. During the time of their stay the progress 
of the natural growth of plants and the increase of their insect enemies 
have provided an abundant larder for the Warbler host. In the spring 
of 1926, while making a bird census, the writer halted before a huge 
hawthorn tree (Crataegus Mollis) and in a few minutes nine varieties 
of Warblers were noted and many members of the several varieties. 

Photograph by Carl F. Groneman 
Woo..ty APHIS 
The tree in question stands out by itself in the forest preserve region and 
on close inspection was found to be infested with thousands of green 
aphids. In addition to the plant lice Warblers destroy great numbers of 
other insects and their eggs. They destroy the larve of the larger moths 
before they have grown to large size. The value of the Warbler throng to 
woodlands is incalculable. Dr. Forbush intimates that even the larger 
birds which apparently need a greater amount of food, are not more 
beneficial than the Warblers, who destroy the insects when they are still 
very small and can be consumed in very much larger numbers. Those 
who are familiar with the rapid spreading of insects when they once get 
