Prior to the field release of natural enemies in bio-control programs, it is essential to evaluate their efficiency under laboratory conditions. One informative method is the functional response of natural enemy tohost density. Moreover, temperature is an important factor that affects the efficiency of bio-control agent. First, the effect of densities of the diaspidid host, Quadraspidiotus perniciosus (Comstock) on functional response types of the aphelinid parasitoids, Encarsia perniciosi  (Tower) and Encarsia citrina (Craw.) was examined. Secondly, we examined the temperature-dependent functional response for the E. perniciosi. Three temperatures (15, 20, and 25°C) and five host densities (10, 15, 20, 25 and 30 scales) were used. At each temperature, 10 to 30 1^st instars were exposed to a female E. perniciosi for a 24 h. In the first experiment, the decelerating rate of decrease in the parasitism rate of E. perniciosi indicated a type II response, whereas the absence of significant dependence on host density by E. citrina indicated a type I response. In the second experiment, E. perniciosi exhibited a type II response (inverse-density dependent parasitism rate) at all temperatures. Therefore, releasing the E. perniciosi in the beginning of growing season on low host populations can provide more control. The attack rate of E. perniciosi increased with increasing temperatures from 15 to 25°C, whereas the handling time decreased. 25°C seems to be the most suitable condition for Encarsia activity and reproduction. This implies that E. perniciosi is well adapted to relatively moderate temperature, which allows its implementation as a bio-control agent of Q. perniciosus during the growing season even in countries of higher latitudes.