Abstract: Apparatus for detecting a specific target odour comprises: a detector unit adapted to have removably associated therewith a holding unit for housing at least one insect in a predetermined position; means for exposing an insect in a holding unit associated with the detector unit to a sample of gas to be tested; and means for enabling monitoring of a response of the insect to the sample thereby to detect a response indicative of the target odour. In use of the apparatus, a holding unit housing at lest one insect that responds in a detectable manner to the target odour is associated with the detector unit. A sample of gas to be tested is supplied to the apparatus, for exposure to the insect or insects in the holding unit. The insect is monitored for a response indicative of the target odour, thus enabling determination as to whether or not the target odour is present in the sample.