65 



bore those crops in 1911. Of the nineteen uninjured fields 14 were 

 under maize in 1912 and the same in 1911, three under grass in both 

 years, one wheat in both years, one rye in 1912 and one oats in 1911. 



Forbes (S. A.). The Chinch-bug Outbreak of 1910-1915.— T^rew^y- 



ninth Report of the State Entomologist of tlie State of Illinois, 

 Urbana, 1916, pp. 71-127, 6 maps, 7 figs. 



The outbioak of BUssus lencoptenis, which began in the autumn of 

 1909 and continued growing in intensity and gradually widening area 

 until the spring of 1915, when it suddenly collapsed, caused a diminution 

 in the yield of maize, wheat and oats amounting to a total value of 

 £1,288, 597. These losses were computed upon a comparison of crop 

 yields and conditions in 17 counties of Illinois; though if the losses for 

 six more counties for the same period be added, the lowest reasonable 

 estimate of the total immediate loss in the three staple crops amounted 

 to £2,600,000. An analysis of the weather conditions for a period of 

 years previous to the outbreak points to a conclusion that the imme- 

 diate cause was unusually hot midsummer weather, with no excessive 

 rainfall, occurring in a region in which the food-plants, especially 

 winter wheat, occupied a relatively large area. The outbreak appears 

 to have been in the nature of an overflow from the heavily infested 

 territory, the direction of which was governed in part by the nature of 

 the crops, but in great measure also by the direction of the prevaihng 

 winds at times when the insects were on the wing, especially in spring 

 when emerging from hibernation, and in the autumn when in search of 

 winter quarters. The outbreak was brought to a conclusion in the 

 spring and early summer of 1915 by heavy rains at a time when the 

 young bugs were hatching. 



B. leucopterus is attacked by some twenty species of predaceous 

 insects, mostly Coccinellids, ground beetles, Rhynchota, and larvae of 

 lacewing flies, as well as the ants, Formica fusca snhsericea and Lasius 

 niger americanus. It is parasitised in the egg stage by Emnicrosoma 

 benefica, Gahan [see this Review, Ser. A, ii, p. 383]. 



The artificial methods of control recommended are the burning out 

 of the insects in their winter quarters and their destruction at harvest 

 time by means of impassable barriers and lines of post-hole traps 

 placed beside infested fields of wheat. Comparing the results of 

 experiments with substances suitable for these barriers, it was found 

 that to be effective, ordinary road-oils had to be applied 41 times in 10 

 days, road-oil No. 6 ten times and road-oil No. 7 only four times. 

 The latter was used in the operations of 1912, but the accidental 

 discovery of the efficacy of crude creosote as a repellent, led to its use 

 in 1913. It was not quite as effective as the road-oil, but sufficiently so 

 to be of great value. 



Experiments are described with kerosene emulsion and Black Leaf 

 40; soap solutions alone, three ounces to the U.S. gallon of water, 

 piroved almost as effective. 



The results of the campaign of 1914 showed that the cost of material 

 and labour used in maintaining 15,000 miles of barrier amounted to 

 £8,100, but this protected an area of 190,590 acres yielding 4,764,750 

 bushels of maize, a fourth of the yield of which, worth £143,000, was 

 due to these protective measures. 



(C346) B 



