Abstract: 【Aim】 In order to better understand the morphology and function of Malpighian tubules of the Cicadomorpha, comparative morphology and ultrastructure of the mute cicada Karenia caelatata Distant and the coleopterous spittlebug Lepyronia coleoptrata (Linnaeus) were investigated. 【Methods】 The Malpighian tubules of adult K. caelatata and L. coleoptrata were observed using both light and transmission electron microscopies. 【Results】 The results show that except the anterior-most segment that takes part in the formation of the filter chamber, each tubule outside the filter chamber of both K. caelatata and L. coleoptrata is morphologically differentiated into four regions, i.e., intermediate duct, proximal segment, distal segment, and terminal segment. Apical parts of the terminal segments in K. caelatata are attached to the ileum, with the posterior-most ends united in pairs and enveloped by a connetcive tissue shortly before arriving at the rectum, whereas the corresponding parts in L. coleoptrata terminate as separated rods and closely attached to the rectum. Ultrastructurally, cells of the tubules in both species possess basal infoldings and apical microvilli. Cells of the proximal segment in K. caelatata possess secretory vesicles, secretory granules, rough endoplasmic reticulum and urospherites. In L. coleoptrata, cells of the proximal segment possess abundant secretory vesicles, and cells of the distal segment contain oval vesicles which appear to fuse with the basal plasma membrane. The microorganisms observed in the proximal and distal segments of K. caelatata are possibly symbiotic bacteria, while those resided in the intermediate duct of L. coleoptrata are likely to be pathogenic. 【Conclusion】 The similarities and differences in morphological characteristics and ultrastructure of Malpighian tubules in the two Cicadomorpha representatives, K. caelatata and L. coleoptrata, not only support the sister relationship of Cicadoidea and Cercopoidea, but also improve our understanding of the functional differentiation of Malpighian tubules in the Cicadomorpha. The discovery of microorganisms in the Malpighian tubules of the two species is informative to the future study of coevolution between the Cicadomorpha and related bacteria and to the biological control of related pests.

Key words: Auchenorrhyncha; Karenia caelatata, Lepyronia coleoptrata, excretory system, symbiotic bacteria, transmission electron microscopy, light microscopy