CHEMORECEPTION OF AMINO-ACIDS BY FEMALE 4TH-INSTAR AND 6TH-INSTAR LARVAE OF THE SPRUCE BUDWORM

An electrophysiological approach was used to record the responses of m axillary styloconic sensilla of fourth-and sixth-instar larvae of the spruce budworm Choristoneura fumiferana to 14 amino acids. One cell in the lateral styloconic sensillum was identified as an amino acid-sens itive neuron. All of the amino acids tested, except 1-proline and 1-ar ginine, were detected by this cell. Arginine did not evoke a response from either the medial or lateral styloconic sensilla. Proline evoked responses from a cell in the medial styloconic sensillum. It is known from previous behavioural work that 1-proline is a phagostimulant and 1-valine inhibits feeding in Choristoneura; we thus further characteri zed the responses to these two amino acids. For both instars, 1-prolin e was detected as low as 0.001 mmol/l and the maximal response was at 50 mmol/l. Stimulation of fourth- and sixth-instar larvae with 1-valin e showed that the maximum firing frequency was obtained at 1 mmol/l. A bove and below this concentration, firing frequency decreases. Sensory responses to the amino acids stimuli did not correlate with known beh avioral responses to similar stimuli.