Determination of parity in populations of dominant Tabanus species (Diptera: Tabanidae) in southeast Texas.

Of 410 females of 11 species of Tabanus collected in south-eastern Texas in 1977, 70.4% were parous and 2.1% biparous and triparous. However, follicle tube dilatations could not be recognised in 58.1% of the parous specimens because they were collected and examined while in the sac stage. Subsequent examination of a mature population of T. nigrovittatus Macq. in 1978 showed that at least 6 days were needed for the follicle tubes of females to reach the yellow-body stage. The data suggested that developmental changes of similar magnitude also took place within the ampullae and terminal follicles after retention of flies in the laboratory for several days after collection. Ampullary widths were unsatisfactory for the recognition of parity because a large percentage of nullipars exhibited enlarged ampullae while many pars had narrow ones.