The bionomics ofScolothrips sexmaculatus(Pergande) (Thysanoptera: Thripidae), an insect predator of spider mites

Abstract

The biology, temperature response, and prey requirements for Scolothrips sexmactllatus were studied in the laboratory with Tetranychus pacificus as the main prey. At 26.7 C and 50% relative humidity, the mean life cycle was 8.9 (range: 7.6-10.3) days; egg, 7.2 days; Ist-stage larva, 2.8 days; 2nd-stage larva, 2.5 days; prepupa, 1.2 days; and pupa, 2.5 days. Male and female immatures developed in the same length of time, but as larvae, killed significantly different mean numbers of prey eggs, 43.0 and 56.0, respectively. Eggs of S. sexmaculatus are inserted into leaf tissue. Larval eclosion lasted a mean 7.6 min, and larvae commenced feeding a mean 40.3 min after vacating the chorion. No larval preference or nonpreference was noted for any given prey stage. Imaginal molts lasted a mean 9.1 min, and the new,adult commenced feeding after a mean 92.7 min. For adult females, no preference or nonpreference was noted for any prey developmental stage. Mating was unnecessary to induce oviposition, which usually commenced on the Ist imaginal day. Unmated females produced only male progeny. Thus, S. sexmaculatus is a facultatively arrhenotokous species. Larval and adult thrips were behaviorally well adapted to preying on tetranychids which produce copious webbing. Thigmotaxes were evident in all instars, and cannibalism did not occur until prey became scarce.

Effect of temperature on life history traits of the predatory thrips, Scolothrips takahashii Priesner (Thysanoptera: Thripidae)

“…m x ϭ(proportion of females)ϫ(age-specific oviposition). constant (188.7 DD) of S. takahashii is higher than the previously reported value for S. takahashii (144.7 DD, Yamasaki et al, 1983), but is slightly lower than that of S. sexmaculatus (209.9 DD, Gilstrap and Oatman, 1976;192.6 DD, Coville and Allen, 1977). These results suggest that S. takahashii as well as S. sexmaculatus has potential to develop over a relatively wide range of temperatures.…”

“…Developmental time (13.3 days) of S. takahashii at 25°C was shorter than that of S. sexmaculatus (16.1 days, Gilstrap and Oatman, 1976;15.7 days, Coville and Allen, 1977). The lower threshold temperature (11.4°C) of S. takahashii is slightly lower than the previously reported value for S. takahashii (15.2°C, Yamasaki et al, 1983) and that for S. sexmaculatus (14.0°C, Gilstrap and Oatman, 1976;13.1°C, Coville and Allen, 1977). The thermal 516…”

“…In a study of S. sexmaculatus (Gilstrap and Oatman, 1976), no eggs hatched at 18.3°C but most larvae (90.6%) were able to reach maturity at this temperature, and larval survivorship did not decrease even at 40°C. Developmental time (13.3 days) of S. takahashii at 25°C was shorter than that of S. sexmaculatus (16.1 days, Gilstrap and Oatman, 1976;15.7 days, Coville and Allen, 1977).…”

“…In a study of S. sexmaculatus (Gilstrap and Oatman, 1976), no eggs hatched at 18.3°C but most larvae (90.6%) were able to reach maturity at this temperature, and larval survivorship did not decrease even at 40°C. Developmental time (13.3 days) of S. takahashii at 25°C was shorter than that of S. sexmaculatus (16.1 days, Gilstrap and Oatman, 1976;15.7 days, Coville and Allen, 1977). The lower threshold temperature (11.4°C) of S. takahashii is slightly lower than the previously reported value for S. takahashii (15.2°C, Yamasaki et al, 1983) and that for S. sexmaculatus (14.0°C, Gilstrap and Oatman, 1976;13.1°C, Coville and Allen, 1977).…”

“…Only three families (Phlaeothripidae, Aeolothripidae and Thripidae) contain acarophagous thrips (Chazeau, 1985) with various degrees of specialization on mites but all species of Scolothrips appear to be specialized predators of spider mites (Priesner, 1950;Lewis, 1973;Gilstrap and Oatman, 1976;Gilstrap, 1995). Among the species of Scolothrips, the best known and most studied is the North American six-spotted thrips, Scolothrips sexmaculatus (Pergande) (Chazeau, 1985;Gilstrap, 1995).…”