Abstract
The prehensile antennae of larval Chaoborus crystallinus are equipped with seven sensilla that comprise 24 sensory cells. Analysis of their ultrastructure indicates that they represent either mechano-or chemo-receptors. The main chemosensory input is established by a compound sensillum, S15 ("sensory cone" with 15-sensory cells), that is located at the tip of the antennal article (outer ventral claw). Exteroreceptors are the "middle claw" of the antenna, and a small sensillum trichodeum at half the length of the antennal article. Proprioreceptive mechanoreceptors are found in the proximal and distal regions of the antennal article. Comparison of sensillar arrangement and ultrastructure indicates that the ancient sensillar equipment of the culicid type is still present within the highly specialized catching apparatus of C. crystallinus. Compared with Culicidae, chemosensitive input is reduced, while proprioreceptive, mechanosensory input is highly developed. Larvae of Culicidae and Chaoboridae appear to possess a homologous set of antennal senilla that show specializations connected to the different functions of the antennae.