Scaling of the Sense Organs of Insects. 2. Sensilla. Discussion. Conclusion

The second part of our review systematizes the published evidence of scaling of the insect antennal sensory system and provides an allometric analysis of quantitative data for 483 species from 21 orders. The number of antennal sensilla is positively correlated with body size, the values differing by up to three orders of magnitude between the smallest and larger insects. The linear size characteristics of the mechanoreceptor sensilla chaetica are also correlated with body size, with the values differing by up to one order of magnitude. At the same time, the number of the sensillum types and the length and diameter of the olfactory basiconic sensilla reveal no significant correlation with body size. The structural complexity of the composite sense organs seems to limit the size reduction of individual sensory units, so that optimization of the sensory apparatus in miniature insects occurs primarily by reducing the number of structural elements: ommatidia and sensilla. The fine structure of miniature compound eyes is already well known, but there are almost no studies on miniaturization of the antennal receptor apparatus. Structuring the information obtained over several decades and our analysis of the available data have revealed some patterns in the scaling of insect sensory systems.