MATERIALS AND METHODS

Survey studies: Survey studies were carried out in two mango farms located at El-Khatara and Belbais districts at Sharkia Governorate, Egypt. The studies were continued for two successive years, from April 2010 to May 2012. The farms received normal agricultural practices and no chemical control was applied. The studies were conducted in an area of about one feddan of mango, Mangifera indica L. leaves, buds and stem bark were monthly randomly collected from the two districts. The samples were put in polyethylene bags and transferred to the laboratory for carefully inspection. These samples were examined in the same day using a stereomicroscope. Scale insects and mite species were recorded. Mite species were directly mounted in Hoyer's medium and identification together with other necessary information about their habitats and written on labels stuck on the slides.

Biological experiments: To study the effects of different preys on the biology of dominant predaceous mites which seemed to be active in nature at both districts. Pure culture of the cunaxid species, Cunaxa capreolus Berlese was established. It was reared on discs of mango leaves infested with the tydeid mite, Tydeus kochi Oudemans and the citrus brown mite Eutetranychus orientalis Klein as preys for the predator. Cunaxa capreolus was placed over cotton wool in the prepared petri dishes. Water was added daily to maintain suitable moisture for mite development.

The cunaxid mite, C. capreolus was reared on three different prey species. Those preys were mixture of adults and nymphs for E. orientalis and T. kochi, while it reared on eggs of the scale insect, A. tubercularis. Twenty newly hatched larvae for each treatment were confined singly in glass rings of 1 cm diameter and 7 mm deep. The rings were fixed to glass slides and each was covered with another glass slide held in position with rubber bands. When the young reached maturity the both sex were allowed to mate and females were retained to complete their oviposition. The food preference experiments and feeding capacity were carried out at 30±2°C and 70±5% R.H. (Krantz, 1970).

Statistical analysis: The results were statistically analyzed by using the analysis of variance according to Snedecor and Cochran (1982) using the computer program SPSS (1997).

RESULTS AND DISCUSSION

Survey studies: Data tabulated in Table 1 showed the surveying mite species and scale insects inhabiting mango trees during the two successive years (2010-2011 and 2011-2012). The occurrence of seventeen mite species and two scale insects were abundance and distribution completely correlated with environmental conditions. Numbers of the collected mites were five species of suborder Gamasida, ten species of suborder Actinedida and one specie of both suborders Acaridida and Oribatida. All gamasid mites were belonging to family Phytoseiidae. The phytoseiid species were Amblyseius swirskii with high numbers and Amblyseius cydnodactylon with moderate numbers, while the others Amblyseius yousefi, Amblyseius enab and Amblyseius cucumeris were in a few numbers. All species were found on mango trees at both districts.

The Actinedida mites included one species of each family, Tetranychidae (Oligonychus mangiferus), Tenuipalpidae (Brevipalpus obovatus) and Tarsonemidae (Steneotarsonemus sayedi) with a low numbers, Cunaxidae (Cunaxa capreolus) with moderate numbers, Stigmaeidae (Agistemus exsertus), Eupalopsellidae (Saniosulus nudus) with high numbers and Raphignathidae (Raphignathus gracilis) with rare numbers at El-Khatara distract. Three species of Tydeidae were recorded, Tydeus kochi with high numbers, Tydeus oregonensis and Pronematus ubiquitus with a few numbers at both districts.

The suborder Acaridida represented by only one specie Hemisarcoptes malus belonging to the family Hemisarcoptidae with a few numbers at both districts. It was mainly associated with the scale insects A. tubercularis and K. acuminata and might be responsible of their reduction.

The suborder Oribatida, family Haplozetidae ware represented by Xylobates souchnaiensis was observed in low numbers in both districts.

The species of scale insects were collected from mango trees. It represented by two species, A. tubercularis (Diaspididae) with a moderate numbers at both districts and K. acuminata (Coccidae) with a low numbers at Belbais district only.

The present results agrees with those given by Kandeel et al. (1986) who reported that family Hemisarcoptidae is represented by the predator mite, H. malus which was found feeding on eggs and crawlers of scale insects that infested citrus groves. And mentioned that phytoseiid mites, Typhlodromus mangiferus, A. swirskii and Aphis gossypii were most abundant on citrus they added to that these predator mites feed on phytophagous mites and crawlers of scale insects Chrysomphalus aonidum, Lepidosaphes beckii and A. aurantii.

Table 1:	Occurrence of mite species and scale insects on mango trees at El-Khatara and Belbais districts, Sharkia Governorate, Egypt during two successive years (2010-2011 and 2011-2012)
+ + + + +: High numbers, cosmopolitan, recorded in all collected samples, + + + +: Moderate numbers, recorded in about 60% of the collected samples, + + +: Low numbers, recorded in about 30% of the collected samples, + +: Few numbers, recorded in about 10% of the collected samples, +: Rare numbers, recorded in one sample only by 2-3 individuals

Table 2:	Developmental duration of female and male stages of Cunaxa capreolus fed on three different prey species at 30±2°C and 70±5%R.H
Means with different super scripts in the same row differ significantly *p<0.05, **p<0.01, ***p<0.001

Table 3:	Effects of different preys on fecundity and consumption rate of the females of C. capreolus at 30±2°C and 70±5% R.Hs
Means with different superscripts in the same row differ significantly ***p<0.001

El-Halawany et al. (1986) who mentioned that, the predator mite A. exsertus which is widely distributed all over the country, this predator mite specie known by its wide food range on phytophagous mite, scale insects, white flies and pollen grains.

Attia et al. (2012) studies the predaceous mites associated with the scale insects infesting mango trees at Qalubyia Governorate, Egypt. They found that H. malus considered as one of the most biocontrol agent of diaspidid scale insects on mango trees.

Biological studies on Cunaxa capreolus
Life history: Female of C. capreolus passes through one larval and three nymphal stages before reaching adulthood, while male has one larval and only two nymphal stages.

Effects of different preys on developmental periods of Cunaxa capreolus: Data given in Table 2 reported that the predacious mite C. capreolus successfully developed from egg to adult stage when fed on any of the three prey species. The females' life cycle of C. capreolus was longer than males. Female life cycle durations were 28.4, 22.7 and 25.0 days compared with 21.0, 19.0 and 19.5 days for males when it fed on E. orientalis, T. kochi and A. tubercularis, consecutively. The shortest life cycle of both sexes were recorded when predator immatures fed on T. kochi followed by A. tubercularis and E. orientalis. Feeding on T. kochi accelerated the development significantly shorted the predator female life cycle compared with the other preys and distinctly elongated female incubation period. Feeding on E. orientalis elongated adult female longevity of C. capreolus to 30.3 days comparing with 25.5 and 26.0 days on T. kochi and A. tubercularis, respectively. Feeding on A. tubercularis significantly shorted the oviposition period compared with the other preys.

The female life cycle was longest when fed on E. orientalis; while it was shortest fed on T. kochi. This results were agree with those obtained by Zaher et al. (1975) and Taha et al. (1988).

Similar findings have been reported for other cunaxid by Zaher et al. (1975) and Arbabi and Singh (2000) who reported that incubation period was the longest immature stage, lasting 8.5, 9.0 and 8.0 days when fed on the different preys.

De Castro and de Moraes (2010) mentioned that life cycle and behavior of Cunaxatricha tarsospinosa Castro and Den Heyer from rubber trees in Brazil were studied, with Tenuipalpus heveae Baker offered as prey. The egg stage was the longest immature stage, lasting 17.1±1.3 days. Total juvenile development was completed in 33.2±2.8 days. Lifetime fecundity was 12.0±2.2 eggs.

Effects of different preys on reproduction fecundity: Data given in Table 3 showed that preys influenced the total eggs laid per female and the total number of consumed prey. The reproductive rate of C. capreolus obviously reflected the preference of feeding on T. kochi comparing with the other preys. In addition, data showed that the fecundity were significantly lower when fed on A. tubercularis compared with T. kochi and E. orientalis. The female deposited a total number and daily rate average where (52.62 and 2.08; 87.63 and 3.95 and 6.53 and 0.28 eggs) when feeding on E. orientalis, T. kochi and A. tubercularis, successively. On the other hand number of preys consumed were significantly higher when fed on T. kochi and A. tubercularis compared with E. orientalis. Results showed that number of consumed preys obviously differ according to prey type.

During life span the female consumed greater numbers of T. kochi and A. tubercularis and moderate numbers of E. orientalis. They were 272.5 individuals, 260.5 eggs and 192.2 individuals of T. kochi, A. tubercularis and E. orientalis, respectively.

When C. capreolus fed on A. tubercularis were not favorable for egg production which resulted in predator population decrease, while tetranychid and tydeid mite induced population increase which might result in suppression of the prey population density. However, those species needs field investigations.

In addition as it should be obliged to search for its prey and this might increase its importance as a biological control agent.