' WALTER E. GARREY 105 



and Deromyia were also good, but the commoner gray forms of 

 asilidae did not show the reactions with the same constancy. Other 

 forms will be mentioned when used. To obtain the desired difference 

 in illumination, the eyes were coated wholly or in part by asphalt 

 black varnish which forms a hard, brittle, opaque covering. 



Efect of Blackening Both Eyes. — Lyon^^ noticed that house flies 

 with both eyes blinded "show marked loss of equilibrium and often 

 refused to fly or move in a normal manner," if "placed on their backs 

 they would remain there for a long time without making any effort 

 to get up." Similarly we find that Proctacanthus remains quiet after 



Fig. 1. Robber fly (Proctacanthus) under normal conditions, seen from above 



blackening both eyes. When handled, the efforts to escape are feeble 

 and unaccompanied by the vicious biting of normal robber flies.- 

 When stimulated, they move abo'ut in a most incoordinated way and 

 usually topple over on one side or the other. Fhght is without hfting 

 power; they fall to the floor and land on their backs. Efforts to right 

 themselves are feeble, incoordinated, and often ineffectual. When 

 resting on a flat surface, the legs are abnormally extended and the 

 proboscis and ventral aspect of the thorax touch the surface, as if 

 the body weight could not be supported. Butterflies similarly settle 

 to the surface, right themselves with difficulty, and simply flutter 

 about, when thrown into the air, and fall to the ground. 



i^Lyon,^ pp. Ill, 112. 



