| The predatory mite Amblyseius pseudolongispinosus which is widely distributed in China hasmany advantageous characteristics, such as fast proliferation, large amount of hunting, strong ability toadapt, and so on. This predatory mite has a strong ability to hunt many kinds of spider mites, forexample, Tetranychus cinnabarinus and Tetranychus urticae. It has a promising commercialdevelopment prospects, and is an important biological control resources in China. Sex ratio and genderdistribution is one of the important biological characteristics and ecological countermeasures ofarthropods, and it is also an important parameter to describe growth of animal population. Relevantresearch found that some phytoseiid mites can actively adjust their offspring sex ratio to adapt to thedifferent living condition. Studies have proved that the predatory mite A. pseudolongispinosus has theability of actively regulating their offspring sex ratio according to different factors, such as temperature,prey density, predatory mite density, female and male proportion, and so on. In order to furtherunderstand whether there are other factors affect the offspring sex ratios and oviposition of thepredatory mite A. pseudolongispinosus, effects of two different kinds of spider mites and their differentdevelopmental stages, residue left by predatory mites or spider mites on the leaves, and matingbetween two different regional strains of the predatory mite on the offspring sex ratios of the predatorymite A. pseudolongispinosus were studied in the laboratory. The results are as follows:1. The effect of the different developmental stages of two different spider mite species on theoffspring sex ratios, oviposition and prey preference of the predatory mite Amblyseiuspseudolongispinosus was studied in the laboratory. The results showed that the offspring sex ratio in A.pseudolongispinosus is always female-biased whatever it’s feeding on. As Tetranychus cinnabarinuswas offered as prey, A. pseudolongispinosus had the highest female percent of progeny (70.34%) whenfed on its all developmental stage, but65.56%and63.32%, respectively, when fed on eggs and nymphs.The lowest female percentage of progeny (56.84%) occurred when fed on larva. As T. urticae wasoffered, the female percentage of progeny was68.34%and70.24%respectively, when predatory mitefeeding on egg and all developmental stage,64.05%on nymph and59.30%on larva. There was asignificant difference among them. To the different developmental stages of both spider mites, thepredatory mites had a clear preference on egg, followed by nymph, and larva was the most unpreferredprey. The total number of eggs produced by the female of A. pseudolongispinosus feeding on egg,nymph and all developmental stage was significantly higher than that of the female fed on larva. Wealso discussed the relationship between prey preference and sex ratios of offspring.2. Residue left by predatory mite itself after activities on the leaves had no significant effect on theoffspring sex ratios of the predatory mite Amblyseius pseudolongispinosus. After different number (0,5,10) of A. pseudolongispinosus feeding spider mites on the leaves for24h, they and their eggs wereremoved and then a new predatory mite was transferred onto the experimental arena and was culturedfor another two days. The different density of previously transferred predatory mites did’t have significant effect on the female percentages of progeny of the predatory mite, which were64.80﹪,63.51﹪and63.63﹪, respectively, at the density of predatory mites of0,5and10. Average number ofeggs laid per day by the predatory mite were gradually reduced, which were3.75,3.50and3.03,respectively and the last was significantly lower than the fist two with the density of predatory miteincreased from o to10. The total number of eggs showed the same tendency.3. Residue left by spider mites after feeding on the leaves had no significantly effect on theoffspring sex ratios of the predatory mite Amblyseius pseudolongispinosus. After T. cinnabarinus attheir different number of50and100feeding on the leaves for24h, they were removed and the samenumber of their eggs reserved on the leaves. No damage of leaves and the same number of eggs ofspider mites were treated as ck. Afterwards, a new A. pseudolongispinosus female was transferred ontothe experimental arena and was cultured for another three days. The female percentage of progeny ofthe predatory mite were67.36﹪，68.71﹪and70.03﹪, respectively, and there were no significantdifferences between the three. When only30eggs of spider mites were supplied, the total number ofeggs produced by the female of A. pseudolongispinosus was the lowest (10.05). It was significantlylower than those as50or100spider mites were removed after24h feeding activites and then30eggs ofspider mites were transferred into arena., which were12.14or12.67, respectively. The average numberof eggs laid per day by predatory mite showed the same tendency.4. The predatory mite A. pseudolongispinosus mating between different regional strains hassignificant effects on its offspring sex ratios. In the treatment of A. pseudolongispinosus mating betweenBeijing strain (B♀×B♂), it has the highest female percentage of progeny (70.51%), but65.97%and65.66%, respectively, when females of the Beijing strain mated with males of the Sichuan strain (B♀×S♂) and females of the Sichuan strain mated with males of the Beijing strain (S♀×B♂). The lowestfemale percentage of progeny (61.14%) occurred in the treatment of mating between females and malesof Sichuan strain (S♀×S♂). There were significant difference between the three. The total number ofeggs produced by the female of A. pseudolongispinosus in the treatments of B♀×B♂and B♀×S♂(43.32and43.08, respectively) is significantly higher than those in S♀×B♂and S♀×S♂(33.88and28.87, respectively). The highest average number of eggs (3.21) produced per day by the female of A.pseudolongispinosus occurred in the treatment of B♀×B♂. The lowest (2.26and2.07, respectively)occurred in the treatments of S♀×B♂and S♀×S♂. In between it existed in the treatment of B♀×S♂.There were significant difference between the three. In this study, the females in the treatment of S♀×S♂most liked to escape, and it had the highest fugitive rate of60.53%, followed by the ones in thetreatment of S♀×B♂with44.83%and of B♀×S♂with19.35%. The lowest occuried in the treatmentof B♀×B♂with9.7%.5. The offspring sex ratio in A. pseudolongispinosus is always female-biased under all conditionswhich is the same with the results before. The variation of some conditions can cause variation ofoffspring sex ratio of A. pseudolongispinosus more or less. A. pseudolongispinosus maintain its population growth by increase their female sex ratio and number of eggs per female when underfavorable condition. |
PDF Full Text Request