234 OHIO EXPERIMENT STATION: BULLETIN 332 



During the course of very severe outbreaks, particularly if 

 accompanied by seasons unfavorable to tree development, thousands 

 of locust trees die. Plate XXXII, Fig. 5, illustrates such an area. 

 The attacks invariably are more severe on upland than lowland 

 trees, and the tops of the trees are preferred to the lower branches. 



Food plants. — The black locust is the preferred and most se- 

 verely injured host. However, several instances have come under 

 the observation of the writer in which cultivated apple trees have 

 been attacked violently. Apples are most susceptible to injury if 

 growing in the immediate vicinity of locust groves and when late 

 frosts kill the tender locust foliage after the beetles have emerged. 

 The insects then turn their attention to the apples while the new 

 locust foliage is coming on. During the seasons of 1912-13 apples 

 in the vicinity of Marietta were injured to a considerable extent by 

 the feeding of adult beetles. 



Soybeans in southern Ohio were observed in 1912 by E. R. 

 Secrest, of this Station, to be severely injured by beetles. 



In addition to the foregoing records, the following hosts either 

 have been observed by the writer or have been reported as attacked 

 by the adult beetles ; dogwood, red elm, white elm, oak of various 

 species, beech, wild cherry. Wistaria leaves, hawthorn, red clover, 

 hog peanut {Falcata comosa) and raspberry. 



Distribution. — ^The locust leaf miner occurs in greatest abun- 

 dance in Ohio in the southern part of the State, though it is found 

 sparsely distributed over the other sections. According to other 

 writers the western and southern limit of its range is Missouri and 

 north to and including parts of Canada. 



Natural enemies. — Agencies of natural control have much influ- 

 ence in regulating the numbers of this pest. Usually one or two 

 seasons of excessive abundance of the locust leaf beetle are followed 

 by a number of years of comparative scarcity, and it is supposed 

 that the natural enemies of the species are responsible for the sud- 

 den reduction of numbers. However, but little is known of these 

 natural control processes. 



The young larva of the wheel bug {Prionidiis eristaUis) is 

 reported to feed upon larvae and adults of this species and in addi- 

 tion the following Hymenopterous parasites have been reared, the 

 report of which is extracted from Cotton (Bui. 7, Ohio Dept. Agr.) 



"Trichogramma odontotae How. Reared from egg masses. 

 In nearly every case where one egg was parasitized, all of the eggs 

 in the mass were similarly attacked. The adult parasite gnaws 

 its way through the leaf, emerging from the upper surface." 



