Chronic electrode for long-term electrophysiological recording from insect chemosensilla.

Insertion of a chronic, non-damaging Pt electrode for electrophysiological recording from chemosensilla in Phormia is described. The experimental procedure did not modify in a significant way the survival capabilities or the general behaviour of the operated insects as compared to control, untreated ones. This method, which allows the performance of subsequent tests on the same specimen up to its full lifespan with fairly constant results, proved to be suitable in long-term experiments on the chemosensory function of insects.

Mechanism of JH influence on the function of labellar chemosensilla in Phormia: experimental suggestions.

The aim of this research study was to determine at which level the JH effect of increasing chemosensillar sensitivity in Phormia could take place. Two-day-old adult female Phormia regina (Meigen) flies were used. Variations in electrical resistance and spike firing frequency of labellar chemosensilla stimulated with NaCl solutions were measured before and after topical application of a JH analogue (JHA). Variations in the above two parameters were also determined in a group of control flies. Results showed that an inverse linear relationship exists between electrical resistance and spike firing frequency in both JHA-treated and control flies. On this basis, we conclude that the above sensitivity variations depend on a mechanism common to both groups of flies. As regards the mode of action of this mechanism, we suggest that JH may influence the mucopolysaccharide secretory function of the accessory cells, the activity of which seems to account for changes in electrical resistance and therefore in sensitivity of the labellar chemosensilla.