ON HORNET SILK AS A PHOTODETECTOR - CONSIDERATIONS OF CURRENT, VOLTAGE AND RESISTANCE .1.

Electric measurements carried out on the silk caps formed by hornet la rvae prior to their pupation have shown that under optimal conditions (30 degrees C and 90% relative humidity) there were significant, albei t reversible, differences between the silk response to visible light v s. darkness. Thus, following electrical charging under illumination, w e obtained current value of a few nA only, a voltage ranging from doze ns to hundreds of mV and a resistance ranging from hundreds of k Omega to several G Omega. Contrarywise, in darkness, the equivalent values were dozens to hundreds of nA, a voltage of dozens of mV and a resista nce ranging from several dozens to several hundred k Omega. Insofar as these values were concerned, the transition was almost immediate upon a change in the illumination intensity of about 15,000 Lux/cm(2). On the basis of these measurable values, the amount of electric charge co uld be computed in Coulombs, whereupon the efficiency was found to be greater by 1 x 10(3) - 1 x 10(5) in the dark than in light. The biolog ical rationale underlying these properties and the sharp transition in response to light and darkness are discussed.