Comparisons of fecundity and tertiary sex ratio between thelytokous and arrhenotokous females of Thrips nigropilosus Uzel (Thysanoptera: Thripidae)

Abstract

Prevalent mode of reproduction of wild populations of Thrips nigropilosus Uzel was examined in Wakkanai City, Japan. Furthermore, reproductive schedule, fecundity, and tertiary sex ratio were compared between thelytokous and arrhenotokous T. nigropilosus. Percentages of thelytokous adults in adult females of the Wakkanai population were 4.0% in October 1992, and about 0.8% in July 1994. Significant differences between thelytokous and arrhenotokous races were not observed in the duration of pre-ovarial maturation, oviposition periods and longevities of adult females at the 18°C and 15L-9D condition. The mean numbers of eggs deposited by thelytokous and arrhenotokous females were ca.63 and ca.142 at the same condition, respectively. The hatchabilities of eggs deposited by thelytokous and arrhenotokous females were not different from each other. The tertiary sex ratio (% male) from once-mated arrhenotokous females was about 23.6%. Net reproductive rate of the once-mated arrhenotokous female tended to be higher than that of the thelytokous female, while intrinsic rates of natural increase of them were not conspicuously different from each other.