INSECT PESTS OF OHIO SHADE AND FOREST TREES 211 



friends of man ; the secondary, his enemies because they prey upon 

 his parasitic friends; the tertiary, his friends because they prey 

 upon the parasites of his parasitic friends; and the quarternary 

 his enemies, because they prey upon the parasitic enemies of the 

 parasites of his parasitic friends. 



A few predaceous enemies are known to feed upon one or more 

 stages of the insect but these are not of great importance. Two 

 Dermestids and some of the stink bugs are known to be of some 

 value. Occasionally the latter may be found in considerable num- 

 bers, as shown by Plate XVIII, Fig. 6. 



Infectious bacterial diseases constitute one of the important 

 natural controls for this species in Ohio. When conditions are 

 prime for the incubation and spread of the disease, hundreds of 

 dead and putrefying tussock larvae may be found in heavy infesta- 

 tions. One of the most striking instances to come under the 

 author's observation was in 1914. A clump of witch hazel (Ha- 

 mamelis virginiana) in Rockefeller Park, Cleveland, Ohio, was 

 defoliated, as indicated by Plate XIX, Fig. 1, by the first brood of 

 caterpillars. The photograph shown was taken in early July. In 

 other parts of the city, where the attack had been similarly severe, 

 the hosts bore great numbers of cocoons and egg masses at that 

 time. This clump drew one's attention when driving by ; for, while 

 the scourge was so severe that defoliation resulted, the cocoons and 

 egg masses were not in evidence. Detailed examination revealed 

 the fact that scarcely a specimen of either was to be found, but on 

 the other hand the ground beneath the shrubs was heavily sprinkled 

 with the dead and shriveled bodies of the caterpillars. 



Specimens were submitted to Dr. G. H. Chapman, then of 

 Bussey Institution, who reported that the infection was in every 

 apparent respect identical with the "wilt" disease of the gipsy 

 moth. So complete had been the destructive work of the disease 

 that no second brood of caterpillars appeared, and the second crop 

 of foliage on the witch hazel was not molested. By early fall the 

 clump presented a normal appearance, as indicated by Plate XIX, 

 Fig. 2. 



Control. Spraying with poison is the cheapest, most effective 

 and most generally satisfactory method of control. As will be 

 pointed out later, under special conditions this method may be 

 supplemented or even supplanted by other measures, but in the 

 main, it is in the poison sprays that we place the greatest depend- 

 ence. 



