202 *" /oHIO EXPERIMENT STATION: BULLETIN 19* 



EXPLANATION OP PLATE I. 



Fig. 1. The oyster shell bark louse much enlarged. 



Fig-. 2. The oyster shell bark louse enlarged two diameters. 



Fig. 3. Branch of horse chestnut defoliated by oyster shell bark louSe. 



Fig. 4. Scurfy bark louse much enlarged. 



Fig. S. Scurfy bark louse, enlarged two diameters. 



