In this method the toxicant is absorbed with blood serum onto a loose roll of chromatography paper; first-instar larvae of Lucilia cuprina (Wied.) are inserted into the air spaces of the roll and allowed to feed. Mortality of the larvae is assessed 24 h later. Typical results using diazinon, dichlofenthian and chlorfenvinphos against susceptible and resistant strains of L. cuprina showed larvae to have resistance factors 6-8 times higher than those for adults determined by established techniques.

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Since 1956, samples of Lucilia cuprina (Wied.) from many parts of New South Wales have been tested annually for signs of resistance to organophosphours insecticides, which are used there to prevent fly-strike in sheep. For tests, 0.1 μg. diazinon per fly was applied topically; this discriminating dose was twice that required to kill 100 per cent. of susceptible flies. In 1965, some of the flies in a sample from Dubbo, in central-western N.S.W., survived the discriminating dose. Sensitivity tests of the progeny of the survivors (DB strain) and of a normal susceptible strain revealed that the LC50 of the DB strain was about three times that of the normal one. Further tests established that a roughly similar change in sensitivity had ocurred to other diethoxy (dichlofenthion, fenthion-ethyl, bromophos-ethyl, parathion) and to dimethoxy (fenchlorphos, parathion-menthyl, bromophos) organophosphors compounds. The change was therefore non-specific and, since it was also small, is regarded as an example of tolerance rather than of resistance.Subsequent field surveys in 1965–66 showed that tolerance of L. cuprina to diazinon was widespread in N.S.W. The possibility that resistant strains will be selected out by continued use of organophosphorus insecticides is discussed.

Strains of Lucilia cuprina showing resistance to dieldrin and aldrin appeared in Australia after 3 years successful use of these insecticides. In the laboratory these showed a “resistance spectrum” similar to that of Anopheles gambiae, Cimex lectularius, Pediculus humanus and Musca domestica. Zusammenfassung DAS RESISTENZSPEKTRUM EINES DIELDRINRESISTENTEN STAMMES DER SCHAFSCHMEISSFLIEGE (LUCILIA CUPRINA WIED.) In Austrafien waren Dieldrin und Aldrin ctwa drei Jahre lang erfolgreich zum Schutz von Schafen gegen die Schmeißfliege Lucilia cuprina angewendet worden, als Fehlschiäge infolge eiasetzender Resistenz aufzutreten begannen. Stämme normaler und resistenter Schmeißfliegen wurden gezüchtet und im Laboratorium untersucht. Zweigkolonien einschließlich eines durch Selektion bereinigten resistenten Stammes wurden nach London gesandt und Kreuz‐Resistenzmessungen vorgenommen. Das sich ergebende Resistenzspektrum für die BHC/Dieldrin‐Gruppe der Insektizide enwies sich ähnlich dem von vier anderen Insektenarten, nämlich Anopheles gambiae, Cimex lectularius, Pediculux humanus und Musca domestica, die den gldchen Resistenztyp entwickelt haben. Das weist auf einen ähnlichen Abwehrmechanismus hin.