1918 ENTOMOLOGICAL SOCIETY. 89 



Insects and Birds. 



When it is known that about two-thirds of the food of our common birds 

 consists of insects, it becomes evident that the agency of birds in the control 

 of insects is of the highest importance. The seasonal diet of the robin, blue 

 bird, catbird, king-bird, flycatchers, chickadee, wren, swallow, woodpecker, cuckoo, 

 night-hawk, warblers, oriole, and the other birds has been carefully studied in 

 recent years, with the resulting discovery that insects form in most cases their 

 only food, and only at certain seasons are small fruits eaten. 



Birds are no doubt of special value to the farmer in nipping incipient 

 scourges in the bud on account of their ability to move rapidly from place to 

 place in search of food, and on account of their varied character and habits. 

 Especially is this true of our winter birds which search every cranny and nook 

 for the hibernating forms of insects at a season when every form destroyed 

 means in most cases the alisence of hundreds of thousands of their progeny the 

 following summer. 



Insect Behavior Toward Stimuli. 



In; recent years a large mass of facts regarding the behavior of insects to 

 their environment — both organic and inorganic — has been accumulated, and in 

 a few cases this information has been of service in the control of injurious forms. 

 In general, however, the application of such methods of control is still in its 

 infancy stage, but it gives promise of valuable results in the near future. 



As the relations of insects to plants and to other insects have been discussed 

 in previous sections, attention will be confined here to the behavior -of insects 

 under the influence of environmental stimuli euch as light, heat, moisture, 

 chemical contact, winds, etc. 



For some time it has been known that plants show tropistic movements with 

 regard to light, heat, gravity, moisture, contact, etc. Moreover, some progress 

 has been made towards an understanding of the processes. Plants, for example, 

 bend towards the light because the cells on the side away from the light grow 

 faster than those on the side next the light. There is no conscious control of 

 the movement by the plant. Animals, too, exhibit movements under the influence 

 of tropic, or rather, taxic stimuli. In the case of insects, butterflies, bees, house 

 flies, and many moths and caterpillars are positively phototropic or photo tactic, 

 and move towards the light, while maggots, bed bugs and cockroaches move away 

 from the light. 



Again, most moths move away from sunlight but move towards a lesser 

 light such as electric or oil lamps. Davenport explains this difference by saying 

 that " butterflies are attuned to a higli intensity of light, moths to a low intensity.'^ 

 Loeb explains the circling of moths and other insects about a light. The stimulus 

 orients the insect by its more intense action on the muscles next the light, and 

 the insect then moves towards the light. 



Loeb states, that caterpillars of the Brown-tail Moth as they emerge from 

 hibernation in spring are positively phototaxic, but after they have eaten this 

 response disappears, showing that taxic reactions are sometimes dependent on 

 the state of the body. 



" Swaine finds that the destruction of piled logs by the wood-boring larvae of 

 the sun-loving Monoliammu.'^ can be prevented by forming a dense shade over 

 the logs by means of brush. In his study of the army cut-worm (Euxoa auxiliaris) 

 in Alberta, Strickland found that the larvae are negatively phototropic and hide 



