oa Journal of the Entomological Society of Southern Africa - The ratios of the femur, tibia, tarsusand tarsal segments, and their value in the demarcation of the genus afronurus lestage

Volume 1968, Issue 10
  • ISSN : 0013-8789



One of the main criteria employed by Lestage (1924) in the separation of the genera Ecdyonurus/Heptagenia and Afronurus, is the relative length of the femur, tibia and tarsus, and the comparative lengths of the tarsal segments in each leg, which he (Lestage) maintains should be taken into consideration, since these dimensions form the basis on which the ecdyonurid group was established. Although the number of adult male and female specimens in my possession is inadequate for a reliable statistical evaluation of the leg formulae laid down for the genus Afronurus by Lestage, the data presented in Tables 1 and 2 appear to justify the following preliminary conclusions. The ratios of the leg segments are subject to greater variation than Lestage must have anticipated. The formulae given by Lestage for the first leg of the Afronurus males viz. tarsus < femur < tibia, approximately applies only to peringueyi (Table I). The species barnardi (Cape) and harrisoni (Cape) also approach this formula but oliffi, barnardi (Transvaal and Natal) and scotti agree better with Lestage's formulae for Heptagenia. The ratios of the tarsal segments (Table 2), likewise, are not constant for the genus.

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