284 



examples of this are cited. Algeria has been invaded in this manner 

 by pests imported from France, such as the woolly apple aphis 

 (Eriosoma lanigerwn), the red scale {Chrysom])halus minor), etc. 



The usual preventive measures against such importations are 

 reviewed, together with a detailed description of fumigation of imported 

 stock by hydrocyanic acid gas, as practised in Algeria, the United 

 States and elsewhere. The formula recommended for its preparation 

 is : cyanide of potassium, 98 per cent., 1 part ; sulphuric acid, 66° Be. 

 1 part ; water, 3 parts. 



Kelly (E. 0. G.). The Green-bug {Toxoptera grmninum, Rond.) 

 Outbreak of 1916. — Jl. Econ. Entom., Concord, N. H., x, no. 2, 

 April 1917, pp. 233-248. 



This paper reviews the various outbreaks of Toxoptera grmninum, 

 Rond., during the years 1908-1915. America suffered from four 

 disastrous outbreaks of tliis pest, in 1890, 1901, 1907 and 1916. 

 Investigation has shown that this Aphid is present in the fields in 

 more or less abundance at all times and is ready to increase with the 

 slightest favourable opportunity. The most important factor in its 

 increase seems to be favourable weather conditions and these appear 

 to be a mild, wet autumn, productive of much self-sown wheat, and 

 a mild winter, followed by a cold and rainy spring. 



The outbreak began in the spring of 1915 and, conditions continuing 

 favourable to the insect, serious infestation during the spring of 1916 

 became inevitable. Strenuous efforts were made to cope with the 

 threatened invasion ; the most hopeful method of control was 

 considered to be by means of parasites, and as Aphidius testaceipes, 

 the most abundant parasite of T. graminwm, was found in great 

 numbers in one field and also occurred scattered over several States 

 many hundreds of thousands of these parasites were collected and 

 liberated in the infested fields. Unfortunately, weather conditions 

 were adverse to the parasites in the fields and their dispersion proceded 

 slowly. Towards the end of May the Aphids were so numerous that 

 the air seemed full of them and street lights were dimmed by them. 

 The general direction of flight was always with the wind. Many of 

 the winged forms carried larvae of A. testaceipes. At the end of May 

 and through early June the weather became warm and dry. The 

 Aphids, having devastated some 600,000 acres of oats and 300,000 

 acres of wheat in Kansas and Oklahoma, had used up their preferred 

 food-plants and the wingless forms, being unable to travel far enough 

 to reach uninfested fields, succumbed, while the wdnged forms became 

 dispersed among other host-plants, chiefly maize and kafir corn. 



Pakks (T. H.). a County-wide Survey to determine the Effect of 



Time of Seeding and Presence of Volunteer Wheat upon the Extent 



of Damage by the Hessian Fly.— Jl. Econ. Entom., Concord, N.H., 



X, no. 2, April 1917, pp. 249-253. 



Durmg the year 1916 an extensive survey was conducted m Kansas 



in connection with the Hessian fly, Maijetiola destructor. The 



entomologists of Kansas Experiment Station have always advocated 



four conditions for successful wheat-growdng, namely, thorough 



preparation of the seed-bed, destruction of self-sown wheat, sowing 



