The nematomorph species Chordodes festae Camerano, 1897 and C. peraccae (Camerano, 1894) are redescribed by using scanning electron microscopy (SEM). C. festae has a cuticle with four different areolar types, the crown areoles being the most noticeable with long spiniform processes. The terminal end in the male specimen has two short lobe-like structures and a ventral groove. C. peraccae has three areolar types in which, as in C. festae, some areoles form groups surrounding the crown areoles. Intraspecific variations were found in body length and body colour in both species and, in C. peraccae, also in the cuticle.

There are numerous open questions concerning the life cycle of Gordiida (Nematomorpha), especially about egg development and viability of larvae during winter, when the temperature of freshwater environments where they inhabit is low. On the basis of experimental studies we demonstrate that egg development of Chordodes nobilii takes 20-25 days at 22°C and 45-55 days at 5°C. We also observed that larvae of C. nobilii obtained from egg strings at 5°C and maintained at that temperature during six months remained inside their egg shells as a survival strategy.

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Thirty-five species of Chordodes have been reported from Africa. The original description of several of these species is incomplete and needs reinvestigation by scanning electron microscopy (SEM) which allows the observation of fine structural details. We reinvestigated five of these species: Chordodes gariazzi, C. heinzei, C. kolensis, C. muelleri, and C. ruandensis. All of them show crowned areoles occurring in clusters. These clusters are formed by crowned areoles that are surrounded by another areolar type. The females of C. kolensis and C. muelleri have polymorphic crowned areoles with both short and long filaments; these areoles are only observed along the ventral groove. Chordodes gariazzi, C. heinzei, and C. muelleri have five areole types, C. ruandensis has three different types of areole, and C. kolensis displays a sexual dimorphism where males have six types of areole and females have seven areole types. Chordodes gariazzi, C heinzei, and C. muelleri have tubercle areoles. Host data and a new distribution record of C. kolensis are reported.

Taxonomic characters of both male and female horse-hair worms, Chordodes balzani Camerano, 1897 (Nematomorpha), are re-described using scanning electron microscopy with freshly collected material. The features are compared with the original description. Chordodes balzani cuticle has six different areolar types. The paired crown areoles, characteristic of Chordodes, are surrounded by other areoles forming clusters. Sexual dimorphism was found in the cuticular pattern, the female showing two different types of crowned areole with a distinct distribution pattern while the male has only one type of crown areole more generally distributed over the body surface. These data are compared to other Chordodes species that have been studied. The sexual dimorphism described here appears to be consistent for the Neotropical species. Host information and new distribution records are reported. A neotype is erected as the original material cannot be traced.