Physiological age was determined for 464 females of 10 tabanid species captured in Manitoba traps in the Swiss Jura. Based on a parity study, Haematopota pluvialis, Haematopota crassicornis and Hybomitra kaurii appear to be autogenous in this locality. Parity was also determined for Hybomitra bimaculata, Hybomitra micans and Tabanus bromius to discern temporal variations. At the beginning of the season the number of nulliparous specimens was too small in comparison to the number of parous

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... s captured later. This suggests the coexistence of autogenous and anautogenous individuals of the same species.