313 



Riley (W. A). Division of Entomology and Economic Zoology. — 



29th Ann. Kept. Minnesota Agric. Expt. Sta., 1920-21, Univ. 

 Farm, St. Paul. 1921, pp. 55-60. [Received 11th April 1922.] 



Experiments with baits showed that bran and molasses were very 

 attractive to cutworms, but the addition of fruit essence did not increase 

 the attractiveness. Tests with stored products are being continued 

 to determine the fatal high and low temperatures for insects. Cultures 

 kept at a temperature of 80-6° F. show that Tribolium conftisum, 

 Duv. (confused flour beetle) has distinct dietary limitations, which 

 may be measured by recording either the death-rate or the time of 

 metamorphosis. The death-rate curve of beetles in a " s^'nthetic 

 flour " is almost identical with that in wheat flour, but the metamor- 

 phosis shows a retardation of ten days or more when compared with a 

 culture of wheat flour. These insects will therefore be used to indicate 

 certain dietary deficiencies in wheat flour substitutes, etc., as soon as 

 more data are available. The numbers of Tribolium seem to be dis- 

 tinctly reduced by the presence in the body cavity of a coelomic 

 Coccidium, which is being investigated. 



In forest entomology, experiment has shown that insects working 

 in logs are much more subject to the action of external ph^'sical factors 

 than was formerly supposed. Logs in deep shade are apparently 

 less liable to injury by the more serious pests than those in more open 

 situations. This is partly due to a retarding of the rate of development 

 in a shady place and partly to the fact that fewer eggs are deposited 

 in logs under very shady conditions. This suggests the possibility of 

 shading logs to protect them from insect attack. It has been shown 

 that the subcortical temperature of logs exposed to the sun may rise 

 to 140° F. or more [R. A.E., A, vhi, 365], and in some logs the tem- 

 perature on many bright summer days will pass above the point 

 fatal to insects. This, however, is not true of all logs. The temperature 

 beneath the bark is governed b}' light intensity, angles of incidence 

 of the sun's rays and many other factors. White pine logs often reach 

 very high temperatures, while Norway pine logs are comparatively 

 cool. 



During a study of the specific toxicity of various arsenicals, it was 

 found that all the common metallic arsenicals may be made into a 

 form that carries a positive electric charge when wet, examples being 

 lead, zinc, copper, calcium, magnesium, chromium, iron and aluminium. 

 Acid arsenicals, such as acid lead arsenate, cannot be made with a 

 positive charge without first converting them into the basic form. 

 Most metallic arsenicals with a positive charge can onlv be obtained 

 by the use of a salt of the metal and a weak acid. Basic lead arsenate 

 will not adsorb an ion of the metal from lead nitrate, but will form 

 lead acetate. In general it is not yet understood whether the metallic 

 ion is adsorbed by the metallic arsenical, or whether the latter adsorbs 

 a metallic hydroxide or oxide complex. Possibly both reactions occur, 

 but sufficient data are not available to state definitely what actually 

 takes place. 



In a shipment of 3,000 narcissus bulbs from HoHand in 1919, 20 

 per cent, were found infested with the narcissus fly, Merodon equesiris, 

 F. ; some also showed infestation wdth larvae of the lunate onion fly, 

 Ettmerus strigatus. Fall. This is a serious pest of onions in Europe, 

 and it is feared that some may have escaped interception ; if so they 

 will constitute a new onion pest in Minnesota. 



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