Comparative Morphology of Wax Gland Heads in Adult Dustywings (Insecta: Neuroptera: Coniopterygidae).

Simple Summary: Most of the body and wings of mature adults of most species of dustywings (Neuroptera: Coniopterygidae) are covered with a superficial coating of pale waxy particles. This white-to-gray waxy 'dust'—from which the common name of the family derives—is secreted onto the outside of the body by wax glands that open on the head, thorax, and abdomen. Each gland opening produces a pair of tiny, curled wax filaments, which eventually break off as minute wax rings. The rings are subsequently distributed across most of the body and wing surfaces by the insect's legs. Within the order Neuroptera, coniopterygids are unique in this form and use of waxy compounds, and it constitutes a distinctive shared feature of species in the subfamilies Aleurop-teryginae and Coniopteryginae (wax glands are apparently absent in the subfamily Brucheiserinae). Despite the interesting adaptive features that this system implies, wax production and its associated morphological features and behaviors are poorly known and rarely studied. In this paper, we examine the comparative morphology of wax gland head ultrastructure in 2 subfamilies, 9 genera, and 28 species of dustywings—the most diverse sample of dustywing taxa examined to date for this morphological feature. We report similarities and differences among the examined taxa and identify ultrastructural characters useful for taxonomic and phylogenetic differentiation at higher levels within the family. In the largest comparative study of coniopterygid wax gland head morphology to date, we used scanning electron microscopy to illustrate the ultrastructure of gland heads found in 2 subfamilies (Aleuropteryginae and Coniopteryginae), 5 tribes (Aleuropterygini, Coniocompsini, Coniopterygini, Conwentziini, and Fontenelleini), 9 genera (Aleuropteryx, Coniopteryx, Coniocompsa, Conwentzia, Cryptoscenea, Heteroconis, Semidalis, Spiloconis, and Thecosemidalis), and 28 species of Palearctic and Oriental dustywings collected from a variety of sites across China. We propose a new descriptive terminology to concisely characterize the major elements of gland head ultrastructure and then identify similarities and differences among them and provide detailed descriptions of the wax gland heads found in each of the nine genera examined. Based on the range of taxa examined, we propose hypotheses about the functional morphology of some of the ultrastructural elements examined and relate them to wax ring formation in dustywings. An identification key for the examined genera based on gland head morphology is also presented. [ABSTRACT FROM AUTHOR]