Sugar Beet Webworm True Army Worm 





Fig. 14. Cross Section through Burrow of the Solitary Wasp 

 Robber-flies 



There is a family of flies commonly known as robber-flies (Fig. 12, 

 Plate VI, Page 21), the members of which prey upon other flies, as well 

 as upon bees and their near relatives, small flying beetles and moths. 

 These flies will often be noticed resting on the ground or some object 

 which furnishes a clear view of the surroundings, patiently waiting for 

 some victim to appear. Their heads are joined to the body by a freely 

 moving neck so that they can be moved at will. While waiting for some 

 ill-fated fly to appear the head is moved about following the flight of 

 passing insects in really human fashion. 



These flies capture their victims by pouncing upon them in true bird 

 of prey fashion. Holding the victim with their long legs, the beak is 

 thrust into its body and the contents sucked up. One of these flies was 

 observed to capture and feed upon a webworm moth. 



(b) TRUE ARMY WORM 



(Figs. 21, 22, 24 and 25, Plate I, Page 11) 



The true army worm is one of those insects which, while always 

 present in small numbers in our fields, commonly escapes, unobserved, 

 because of its seclusive habits. However, when for any reason the natural 

 checks become abnormally scarce or favorable weather conditions prevail 

 in connection with a plentiful food supply, it multiplies very rapidly, 

 overrunning our fields in vast hordes, often traveling in such large num- 

 bers that the very earth seems to move. All follow the same general 

 direction, destroying crops as they go, and leaving nothing but the 

 riddled remains of what a few days before gave promise of a bountiful 

 harvest. 



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