Parity in a Texas population of Hybomitra lasiophthalma (Macquart)

Parity was examined in a population of Hybomitra lasiophthalma (Macq.), an important livestock pest, inhabiting a floodplain forest on the Navasota River near Bryan, Texas. Of 1031 females sampled from 29 March to 12 May, 62.4% were uninparous, 2.6% biparous and 3.5% nulliparous. The first parous fly appeared on 2 April, and the second 5 days later. Samples of 25 flies from each of 40 of the 45 daily collections made during this period showed that parity increased sharply over the next week to reach 88% on 16 April, after which rates declined in all but 3 cases. One to 4 biparous flies per sample of 25 females were taken from 9 April onwards during the period of adult activity. With the exception of 10 females containing Stage V (fully developed) eggs and entering traps while partially engorged, the follicle tubes of all the females examined showed well-defined relics because they had been kept alive for no less than 6 days before examination. The significance or this practice in enabling definitive recognition of biparous females is discussed.