Behavioural and electrophysiological responses of the phlebotomine sandflyLutzomyia longipalpis (Diptera : Psychodidae) when exposed to canid host odour kairomones

Compounds from the odour-producing glands of the fox Vulpes vulpes were col lected. This complex mixture of compounds was used to stimulate the 'ascoid ' olfactory organs of female sandflies in single sensillum and gas chromato graphy-linked single sensillum recordings. Sixteen of these compounds were identified using gas chromatography-linked mass spectrometry and amounts pr esent were determined. The compounds fell into four organic classes: ketone s, carboxylic acids, alcohols and aldehydes. Specific neurones present in t he ascoid sensillum that responded to each of these classes of compound wer e characterized. A bioassay chamber was developed that gave female sandflie s the choice of two odour sources. Female sandflies were attracted upwind b y fox odour and were trapped in closer proximity to the fox odour port than the control port. Synthetic compounds were recombined in appropriate quant ities to mimic the fox odour. In this bioassay, the synthetic blend attract ed sandflies upwind, and again they were caught closer to the test port tha n the control port. Furthermore, the synthetic fox odour induced an electro physiological response from neurones in the ascoid sensillum that was very similar to that induced by natural fox odour. No synthetic compound alone i nduced the same behavioural response from sandflies as did whole fox odour. However, benzaldehyde, 4-hydroxy-4-methyl-2-pentanone and 4-methyl-2-penta none alone did cause sandflies to fly upwind and to be caught closer to the test port than the control.