Cheleocloeon

Gillies, M. T., 2001, New species of Baetidae (Ephemeroptera) from the Upper River Sigi, Usambara, Tanzania, Journal of Natural History 35 (1), pp. 23-32 : 31-32

Placement of Cheleocloeon in the Bugilliesia group of genera: a criticism

In their discussion of the systematics of Cheleocloeon (Lugo-Ortiz and McCaOEerty, 1997) the authors emphasized that the larvae of the genus were distinguished by the long poorly denticulate tarsal claws and the well-developed medial process of the second segment of the labial palps. This distinctive process [likened by Wuillot and Gillies (1993) to the outline of a crustacean claw] is clearly a shared apomorphy. It is long and pointed in C. yolandae Wuillot and C. carinatum Wuillot from Guinea, intermediate in C. incisum (Crass) from South Africa, and rather shorter and rounded in C. dimorphicum (Soldan and Thomas) and C. sigiense sp. n. from North Africa and Tanzania, respectively. The last-named species diOEers from the others in that the anterior margin of this process is straight not convex.

If the de®nition of the larva of Cheleocloeon can be established with reasonable con®dence, the same cannot be said of the adult. The hind wing has been lost in a number of unrelated lineages of the Baetidae and, as pointed out by Lugo-Ortiz and McCaOEerty (1997), its absence in the female of all known species of Cheleocloeon is unremarkable.

However, the same authors (Lugo-Ortiz and McCaOEerty, 1996) have gone on to describe an association of baetid genera from Africa which they have designated the `Bugilliesia complex’. They de®ne this grouping as distinguished by a conspicuous basomedial protuberance on segment 2 of the male forceps. It is certainly true that the forceps in the genera Bugilliesia Lugo-Ortiz and McCaOEerty, Rhithrocloeon Gillies , Kivua Lugo-Ortiz and McCaOEerty, and Mutelocloeon Gillies and Elouard have undergone reduction and sometimes bizarre modi®cation. But in the other genera incorporated by Lugo-Ortiz and McCaOEerty in the complex, namely Afrobaetodes Demoulin , Potamocloeon Gillies and especially in Cheleocloeon , this protuberance is no more marked than in certain other baetid lineages. For example, Traver (1935) ®gured similar forceps in a number of Nearctic species of Centroptilum Eaton , some of which were later shown by McCaOEerty and Waltz (1990) to belong to Procloeon Bengtsson.

Lugo-Ortiz and McCaOEerty (1996) remark that the complex is not de®nable in the larval stage. Indeed one may go further by pointing out that larval taxonomy provides evidence for the polyphyletic nature of the complex.

Foremost among the elements that indicate the diverse origins of the group is the tibiopatellar suture. The importance of this structure was shown by Kluge and Novikova (1992) and Kluge (1997) who drew attention to a plesiomorphic character shared by members of the Afroptilum group of genera. This character was the contrasting presence of a tibiopatellar suture in the mid and hind legs and its absence from the fore legs (®gure 10). In most other Baetidae , including all the Baetinae, it is present on all three legs. This structure and the taxonomic importance attributed to it by Kluge (1997) is not referred to by Lugo-Ortiz and McCaOEerty (1996, 1997).

Nevertheless, from examination of material in my own collection it can be shown that among the genera included by these authors in their Bugilliesia complex are some with a tibial suture on the fore leg, for example Afrobaetodes and Potamocloeon , and some with a suture on the mid and hind legs only, including Bugilliesia and Cheleocloeon (cf. ®gure 10).

Further evidence of the polyphyletic nature of the complex is provided by the inclusion of the genus Potamocloeon . This genus shares with Cloeon Leach and Procloeon the presence of bilamellate gills on the anterior abdominal terga and of well-developed spines on the lateral margins of the terga, Gillies and Thorpe (1996). Together, they form a group adapted to slow-moving and sometimes still waters.

These ®ndings suggest that the term Bugilliesia complex should be restricted to the rather small group of genera with major reduction of the genital forceps, namely Bugilliesia , Rhithrocloeon , Kivua and Mutelocloeon .