Repellents for Stomoxys calcitrans (L.), the stable fly: techniques and a comparative laboratory assessment of butyl methylcinchoninate

Abstract

An in vitro test, based on the molasses sandwich-bait test, for mass screening of new compounds for general insect repellency is described. This is followed by a detailed account of a laboratory technique for comparing the initial potency of contact repellents for the stable fly Stomoxys calcitrans (L.).Methods for rearing S. calcitrans of standardised aggressiveness and making comparative assessments of contact repellents against this fly are described. For initial potency, a standard area of the treated close-clipped abdominal skin of mice lying outside the cage was exposed through an orifice to standardised flies. A treated 0·5-cm-wide screen was incorporated as a border round the exposed area of treated skin so that flies biting the mouse were obliged to make tarsal contact with repellent. Using this method, and the organdie bag x human hand method for determining persistence on an inert substrate, each of the following repellents was compared with butyl 3-methylcinchoninate, a new repellent for S. calcitrans:dimethylphthalate; 2-ethyl-1, 3-hexanediol; butoxypolypropylene glycol; dibutyl succinate; N,N-diethyl-m-toluamide; di-n-propyl isocinchomeronate; 2,3,4,5-bis (Δ2-butenylene)-tetrahydrofurfural; 2-hydroxyethyl n-octyl sulphide and N-benzoyl piperidine.In each case butyl 3-methylcinchoninate was found to be superior. In the initial potency tests, the 50% repellency application rate was found to lie between 0·002 and 0·007 mg/cm2, while on organdie, rates of 0·2, 0·4, 0·8 mg/cm2 gave mean protection periods of 9, 19 and 34 days, respectively.