| Euseius nicholsi(Ehara et Lee) is an important natural enemy of many species of pest mites,especially of citrus mites.As a common predatory species,it plays an effective role in control of the pest population due to it takes the prey in large quantities with a wide range of the pest species in field conditions.The comparative biology of the predator was systematically investigated using three diets under five constant temperatures.Studies on behavioral responses to odor and facies of host plant of the pest,and reproductive behaviors of the predator were conducted to understand relationships among the predator,the pest and the plant,and within the predator.The major results were as follows:1.E.nicholsi was respectively fed with the pollen of sasanqua,Tetranychus urticae Koch and Tyrophagus putrescentiae(Schrank).The results showed that, although E.nicholsi can prey on egg of T.putrescentiae,it can not complete natural development.Other two were favorable for the growth of E.nicholsi.Its life cycle duration,longevity of the adult female,oviposition duration and and average lifetime fecundity fed with the pollen were 6.18d,24.79d,16.72d and 23.03 consequentially, while that fed with the T.urticae 5.67d,25.72d 18.17d and 25.38,respectively.It showed a trend to increase in the population E.nicholsi under the two diet(?) and the population tendency index(14.28) was highest under the pollen.However,double population time was as short as 3.5201 days in the experimental population feeds on T. urticae in laboratory.2.The development of E.nicholsi(Ehara et Lee) fed with T.urticae Koch was studied at the constant temperature of 19,22,25,28,31℃and 80%RH,and the data obtained were used to determine relationships between the development rate in every stage of the predator and the temperature.The results show that the development period of E.nicholsi,reaching to maximum values(8.96d) at 19℃and minimum value(3.99d) at 31℃separately,are shortened with rising of temperature within the rang of 19℃-28℃but slightly prolonged within 28℃-31℃.The developmental threshold temperatures ofE.nicholsi is 8.59℃,and their effective thermal summation is 83.33 day-degree.The relationship between development and temperature displayed a better fit to the Logistic equation than the linear one.3.The favorite of E.nicholsi to host plant was examined with dwarf bean Phaseolus vulgaris var.humilis and soybean Giycine max.The results show that odor,color and external structure of plant leaves influences the behavior of E.nicholsi. The select rate of the dwarf bean by the predator is highter than that of the soybean. The odor of herbivore-induced plant volatiles is the main factor attracting E.nicholsi though others may affect the selecting bihavor.4.E.nicholsi obvious has learning behavior in finding host plant and preyes. After continued stimulate by odor of both healthy and injured plant with condition of food,the conditioned predatory mites showed a higher choice rate to the plant.It means that experienced mites with volatile substances of the plant are more sensitive to the volatile than those unexperienced.5.E.nicholsi reproduces by amphigenesis and has complicated mating behavior. The male,which won in competition for mating,climbs up backside of female with headfirst direction.Then the male rams body to 180°and its capitulum towards the opisthosoma of the female.Furtherly the male moves towards the ventral of female, and mating take place when the ventrals of both cling to each other.The female carrying the male can walking,preying and drinking during mating.The mites could mate once it emerged so that feeding and drinking are not absolute necessity for mating of the newly emerged adults.The female may lays egg in maximum by mating once only.The oviposition duration and average lifetime fecundity in the female were affected by duration of mating.
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