Sexual size and shape dimorphism (SSD and SShD) are understudied phenomena in millipedes. In the present study, we investigated both kinds of sexual dimorphism in some morphological traits, as well as whether shape of the morphological traits varied more than their size. Three julidan species, viz., Pachyiulus hungaricus (Karsch, 1881), Megaphyllum unilineatum (C.L. Koch, 1838), and M. bosniense (Verhoeff, 1897), were used for these purposes. By means of traditional and geometric morphometrics, we found that SSD exists in linear measurements of the tested morphological traits, as well as SShD of the legs in all analysed species. Also, SSD of antennal centroid size was detected in P. hungaricus and M. unilineatum, in addition to SShD of antennae in P. hungaricus and M. bosniense. Our results indicate that morphological intersexual differences are species-specific and that the shape of some morphological traits varies more than the size of centroids of the same structures.
Two modes of post-embryonic development, hemianamorphosis and epimorphosis, show a distinct pattern among extant centipede (Chilopoda) orders. Although studies on post-embryonic development in Lithobiomorpha date back to the 19th and the 20th century, many ambiguities referring to nomenclature of their post-embryonic stages still exist. In this paper coherent terminology of the post-embryonic stages in Lithobius melanops, which could be applied to other lithobiomorphs, is proposed. Additionally, morphological variability of selected morphological traits was analyzed using traditional and geometric morphometric approaches. We recognized five anamorphic (anamorph 0 to 4) and five epimorphic stages (agenitalis, immaturus, praematurus, pseudomaturus and maturus). Measurement and count of certain morphometric characters, detailed description of genital appendages, shape and size variation of the forcipular apparatus, the cephalic capsule and the terminal legs are given. Moreover, for the purpose of geometric morphometric analyses we separated specimens of epimorphic stages into three groups (agenitalis-, praematurus- and maturus-like) based on the level of differentiation of genital appendages. Sexual size dimorphism of the forcipular apparatus was observed only in the praematurus group. Also, significant inter-group forcipular size and shape differences are found between some tested groups. Furthermore, significant differences in size and shape were recorded for the cephalic capsule between all groups. Finally, significant size differences in ultimate legs are present between all epimorphic groups, while shape differences were detected only between agenitalis and maturus groups. Our results contribute to overcoming terminological disparities and provide guidelines for distinguishing stages via discrete and continuous changes during post-embryonic development of the anamorphic centipede.