Hypothesis on radar sensing and communication by hornets: comments on their antennal organulles and electrical...

Our study shows that the antenna of the hornet is densely covered from base to tip with six types of organulles, namely, a trichoid organulle, about 23 microm in length, a campaniform organulle which is 12 microm long, a heretofore undescribed structure measuring about 9 microm in length which we have now named the Agmon organulle, a rather flattened placoid organulle measuring about 25 microm in length and not projecting on the antennal surface, and finally rounded structures about 3 microm in diameter which are indented in the cuticle and resemble extraretinal photoreceptors. All the above-mentioned structures occur in the workers and drones, and the latter also possess an additional structure, namely, the tyloid which is about 254 microm long. Such organulles as protrude from the antennal surface are mostly orientated distally and their length is about half that of similar organulles on the hornets body. Yet their density on the antenna is greater than elsewhere on the body and in fact on all the antennal segments (12 in the workers and 13 in the drones) the entire surface area seems to be occupied by them. The most numerous are the trichoids, while the other organulles mentioned are fewer in number. In measuring the electric properties of the antennae, we obtained the following values: 10-80 nanoAmpers (nA), 60-100 milliVolt (mV) and several scores of Mega Ohms (Momega) in the dark, as compared to 10-20 nA, 150-200 mV and few Momega under illumination. We found that in many respects, the cuticle in the antenna behaves like an organic semiconductor possessing thermophotovoltaic (TPV) properties. Apart from contemplating that the role of the antennal organulles is as a mechanoreceptor, a chemoreceptor or a combination of the two, we also raise the conjecture that these organulles might serve as elements that pick up and broadcast at submillimetric wavelengths, and that the electric energy extant in the vespan antennae supplies the energy source for this kind of activity.