Comparative morphology of the post-embryonic development reveals the existence of distinct nymphal semaphoronts for Mantodea (Dictyoptera)

SummaryThere is a great knowledge gap regarding the morphology of immatures of Mantodea, making taxonomic identification of the nymphs difficult, therefore hindering their inclusion in other studies. The present work recognizes general ontogenetic patterns shared by praying mantises through the comparative analysis of the post-embryonic changes in the external morphology of the nymphal instars of 10 Neotropical species, representing nine genera in five families. Nymphs were reared in the laboratory, their exuviae were collected and vouchers fixed. A total of 369 specimens and 495 exuviae were studied, and a total of 7000 images of live nymphs, at each instar, were taken. Shared developmental patterns were recognized for the form of the spines of the forelegs, proximal discoidal spine of the forefemora, wing pads, female genitalia, cerci, body adornments such as denticles, lobes and apophyses, and crypsis. Based on the recognition of a set of key differences in these features, two distinct, successive forms are recognized for mantis nymphs: the protonymph, the form of the first instar, and the deuteronymph, the form of the remaining instars. In turn, two successive forms are identified for the deuteronymphs: the mesonymph, the form of the early deuteronymphs, and the metanymph, the form of the late deuteronymphs. Literature data provide good support for the occurrence of the observed patterns also in many other and highly diverse lineages of Mantodea, suggesting this might be a generalized feature, fixed in the ontogenetic system of the order. If so, these nymphal forms can be considered semaphoronts of Mantodea, which are more practical and more relevant references than instars for comparisons between praying mantis nymphs. An original key to recognizing the different post-embryonic semaphoronts and sexes of Mantodea is provided. The discovery has wide application in phylogenetic and taxonomic studies, providing an important framework for the study of nymphs of Mantodea. It is recommended that taxonomic studies provide descriptions for proto-, meso- and metanymphs, and include their features in identification keys.