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beginning of a flight the males predominate, the females appearing 

 after about a week and rapidly increasing in numbers, till at the time 

 of full flight and during its decline, the females are in the majority. 

 The best time for setting the traps is therefore on the first appearance 

 of the females before they have oviposited, the period of usefulness 

 lasting only 15-20 days for each flight. After this time the presence 

 of the traps is not only useless, but actually harmful, since they then 

 destroy predaceous and other beneficial insects. 



Newstead (R.) & DuvALL (H. M.). Bionomic, Morphological and 

 Economic Report on the Acarids of Stored Grain and Flour. — 



Reports of the Grain Pests ( War) Committee of the Royal Society, 

 London, 1918, no. 2, 48 pp., 11 plotes. [Received 18th December 

 1918.] 



This report describes important work on grain Acarids that has been 

 carried out in Liverpool, where grain can be inspected in ship, granary 

 and mill, while research has been undertaken in the laboratory of the 

 University. The harmful species that have been found infesting 

 grain and flour include the Tyroglyphid mites, Tyroglyphus {Alearohius) 

 farinae, DeG., Ghjciphagus cadaverum, Schr., and Chortonlyphus 

 arcuatus, Troup., the last being exceedingly rare. Tyroglyphus longior, 

 Gerv., was not found, and T. aire, L.^ was only once observed in 

 wheat from an unknown source. Cheyletus erudilus is constantly 

 associated with Tyroglyphids in grain and preys upon them, but its 

 numbers are never great. A species of Gamasid also occurs very 

 rarely. The life-histories of the various species were worked out in 

 breeding-cells. 



Tyroglyphus (Aleurohius) farinae is the only Acarid that has been 

 found in flour and is undoubtedly the most serious and frequent of 

 all Acarid pests of grain and flour. It is also a common pest in cheese 

 [see this Review, Ser. A, v, p. 516]. The life-cycle of this mite was 

 worked out in June and July at temperatures from 64° to 71° F. In 

 captivity the female lays from 20 to 30 eggs, 3 or 4 being deposited 

 each day. After an incubation period of 3 to 4 days the larva emerges, 

 feeds and develops rapidly for 3 days and then becomes inert for 1 or 2, 

 after which the larval skin splits dorsally and the nymph emerges. 

 The nymphal stage lasts from 6 to 8 days, when transformation to 

 the adult form occurs. Pairing takes place on the day of ecdysis or the 

 day after, oviposition occurring 2 or 3 days later. The males generally 

 die shortly after mating, though they may pair with several females. 

 The life-cycle thus occupies 17 days in favourable conditions, but in 

 the winter months was found to require 28 days, both the incubation 

 and nymphal periods being prolonged. The attack is made on wheat 

 grains by a small hole being bored in that portion of the epicarp which 

 overlies the embryonic region. The Acarids then enter and devom* 

 first the embryo and its surrounding tissues and later the endosperm, 

 until little is left but the hollow husk. 



Glyciphagns cadaverum frequently occurs in wheat which contains 

 T. farinae, but in smaller numbers. It does not seem to attack sound 

 wheat but lives on broken grains and debris. The life-cycle of this 



(C545 a2 



