Myrsidea Waterston, 1915 (Phthiraptera: Menoponidae) is the most diverse genus of avian chewing lice. Myrsidea has a global distribution, is thought to be highly host-specific, and parasitizes mostly passerine birds. However, the rate of taxonomic studies describing new species is relatively low, and it is thought that much of the diversity of Myrsidea is yet to be discovered. This low rate of taxonomic description for this genus, and many others, may be related to the time-consuming nature of morphological species description and a lack of expertise in louse taxonomy. Furthermore, most of the taxonomic revisions and reviews have focused on specific host families, and no comprehensive review of the morphology and molecular work of Myrsidea has been completed in the last 20 years. Here, we review the taxonomy and systematics of Myrsidea to (i) describe this chewing louse genus and its biological importance; (ii) describe current problems with its taxonomy; (iii) simplify and summarize morphological descriptions; (iv) summarize molecular data; and (v) provide a comprehensive checklist of the Myrsidea species, with all publications and localities of occurrence included. Together, we hope that this information will provide researchers with a single source of information on the genus Myrsidea, making it easier for work to proceed on its taxonomy, systematics, ecology, and evolution. Importantly, our work highlights important gaps in our knowledge of Myrsidea, providing guideposts on where future work on Myrsidea is needed.

Polyneopteran insects have relatively large genomes compared to holometabolous insects, which appear constrained by a threshold of 2 pg/1C DNA. This threshold may be due to costly complex development and higher energy demands. Genome sizes (GSs) are particularly bulky in various species of Orthoptera, reaching sizes up to 18.64 pg/1C DNA, however, recent analyses comparing insect GSs neglected the order Embioptera (webspinners). Our access to fresh specimens of 12 species from 6 of the 13 named taxonomic families provided a chance to determine if embiopterans also support bulky genomes. Flow cytometry results revealed that embiopteran GSs ranged from 2.41 to 7.56 pg/1C, similar to other polyneopterans. Based on previous studies reporting correlations with GS, we tested for correlations between GS and body length using independent contrasts.The ancestral state of the root was estimated at 4.57 pg/1C. A positive relationship was detected whereby larger-bodied webspinners displayed larger genomes, with female Antipaluria urichi (Saussure) (Clothodidae) having the largest genome at 7.56 pg/1C.This GS is approximately 3 times larger than the previously reported embiopteran GS of pg = 2.66 for a male Oligotoma saundersii (Westwood) (Oligotomidae). GS showed no consistent patterns of phylogenetic signal for Embioptera.The underlying causes for large genomes are briefly reviewed.