576 



was by means of a smouldering wood fire for about six hours at a time 

 on three occasions, at intervals of two weeks. 



The maize was shelled at the beginning of January, placed in the 

 sun for two days, sifted to remove dust and chai?, fumigated with 

 hydrogen cyanide for 16 hours and stored in a bin. This storage 

 bin was 7| ft. high and 4ft. square, made of closely fitted boards, one 

 half of the top having a movable cover. The outside was tarred and 

 the inside lined with roofing paper with overlapping edges, and running 

 from the bottom of one side halfway across the floor was a suitably 

 perforated flue that rose vertically through the centre of the bin to 

 within 18 in. of the top. The lower part of the flue held a gas generator 

 fitted with an air-tight door, so that the cyanide fumes could thoroughly 

 penetrate the stored grain. 



As this was put into the bin, muslin bags, each containing 3 oz. 

 crude flake naphthaline, were distributed at regular intervals through- 

 out the mass, though this did not seem to be efficacious in warding 

 off insect attacks. Three cyanide fumigations at intervals of 10 and 

 16 days were applied during February and March, and further fumi- 

 gations with carbon bisulphide in the middle of March and May. On 

 opening the bin at the end of May a large number of weevils were found 

 at the bottom, but the seed was clean and bright, entirely free from 

 mildew, and practically free from weevils and moths, and had an 

 indicated viability of 87 per cent. The experiment proved that 

 hydrocyanic acid gas can safely be used in fumigating thoroughly 

 dry seed maize, Avithout much affecting its vitality. 



Gaeman (P.). Tarsonemus pallidus, Banks, a Pest of Geraniums. — 

 Maryland Agric. Expt. Sta., College Park, Bull. no. 208, June 

 1917, pp. 327-342, 13 figs. [Received 28th October 1917.] 



The more common insect enemies of the geranium are general pests 

 that attack the plant only when compelled to do so from lack of other 

 more suitable food. These include the mealy bugs, Pseudococcus citri 

 and P. adonidum [longispinus), the whiteflies, Aleurodes cilri and 

 A. vaporariorum, and the mites, Tetrafiychus telarius (red spider) and 

 Tarsonemus pallidvs. The latter mite has previously been described as 

 the cyclamen mite [see this Review, Ser. A, v, p. 507], but since it attacks 

 other plants with equally injurious effects, the author suggests the 

 name pallid mite as being more appropriate. T. approximatus is 

 regarded as a synonym of this species, which is closely allied to 

 T. floricolus. The various stages and the life-history are described. 

 Parthenogenesis was proved to occur in the females, the life-cycle of 

 which occupies about 33 days ; the males, which are much less 

 numerous, have a shorter existence. 



A high degree of humidity (80 - 90%) and a temperature between 60° 

 and 80° F. are beneficial to the development of this mite, which usually 

 migrates by crawling from one plant to another when the leaves are 

 in contact. Most varieties of geranium are attacked by T. pallidus. 

 which causes a scorched appearance on the under-side of the leaves ; 

 these ultimately curl up and drop prematurely. Heavily infested 

 plants may lose all their leaves through the invasion of a fungus before 

 they drop. Plants should be v\"e^J spaced out to prevent migration of 

 the mites. 



