الفهرس 
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Taxonomical StudiesOnly 14 pages are availabe for public view
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Abstract
Mites play an important role in the biochemical cycles of nature as well as in the agricultural cycles of organic matter. They are very important both in human and animal catering. According to their feeding habits, the mites occurred on deciduous fruit trees can be classified into three groups (phytophagous, predacious and these of unknown feeding habits). This point has gained an extended attention for the last four decades and mites have won nearly the same fame of importance as insects have. When reviewing previous and current results focused on mite species (both phytophagous and predacious) live on citrus trees in both Egypt and abroad. It was cleared that, there were a lot of species pertaining to diverse groups of mites. So, the current work aimed to study the taxonomy and the ecology of some species with economic importance. In the present study, an accurate survey of mite species inhabiting citrus trees in Assiut city and its suburbs was done. The present study describes three new species, new to science, belonging to three different families of mites (Acaridae, Histiostomatidae and Scutacaridae). Moreover, the present study was designed to explore the ecological trends of certain phytophagous and predacious mite species inhabiting citrus trees under various circumstances. However, the great numbers of species and their various morphological differences acquire more intensive and comprehensive research especially for the predacious ones. Therefore, the author intended to give some morphological and taxonomical treatises. The present work might help acarologists to classify the species of mites found on citrus trees, whether phytophagous or predacious ones. As for the description of the new species, the present survey helped to discover three new species that have not been described before whether in Egypt or around the world. The present course of investigation, therefore, had to be accomplished in the following four points: 1. Survey of mites inhabiting certain citrus fruit trees (citrus orchards) in Assiut Governorate, Upper Egypt. 2. Morphology and taxonomy of some mite species inhabiting citrus orchards. 3. Description of three new species pertaining to the families: Acaridae, Histiostomatidae and Scutacaridae. 4. Exploration of the ecological trends of predacious and phytophgous mite species under different circumstances. The author would like to stress that the present work is principally dedicated to the taxonomy and ecology. For this purpose, the original descriptions were collected and all the drawings of detailed morphological features were examined, especially for the Egyptian mite fauna. The present study included the regular samples collected from soil, leaves and debris under citrus fruit trees, Assiut Governorate, in order to study the mite fauna inhabiting citrus leaves and weeds under the citrus fruit trees. Previous works were reviewed, materials and methods were explained, then results were tabulated, illustrated, discussed and summarized. The thesis was entailed with the English and Arabic summary. This work revealed the following results: 1. Surveillance studies revealed the occurrence of 113 mite species pertaining to 47 families and 83 genera in addition to 4 unidentified genera and species. According to their feeding behavior, mites were divided into three major groups (i.e., 12 species are plant feeders, 76 species are predacious mites and 25 species are of miscellaneous feeding habits). 2. Of the total of mite fauna educed from different localities, three species belonging to the families: Acaridae; Histiostomatidae and Scutacaridae were found to be new to science. These species are: a. Caloglyphus citri Eraky et al., 2017 b. Histiostoma herbali Eraky et al., 2017 c. Heterodispus longisetae n. sp. Based on the morphological characteristics of the collected mite species, the author established identification keys for the Egyptian species of the families reported. The most important results can be reviewed below: 1. General Survey of Mite Species: The survey revealed the occurrence of 113 mite species in total, representing 47 families and 83 genera. According to their feeding behavior mites were divided into three major groups based on their feeding habits. Twelve species are harmful and phytophagous, 76 species are beneficial predators and 25 species have miscellaneous feeding habits. Also, three new species were described, photographed and illustrated. 2. Seasonal and Monthly Abundance of Mite Groups: a. Mesostigmata mites:
The highest population density of Mesostigmata mites was recorded during autumn and spring, while, winter was the least favorable season for Mesostigmata mites flourishing. Two peaks of abundance were recorded in November and April. b. Cryptostigmata mites: The highest population density of Cryptostigmata mites was recorded during autumn and winter, while, summer was the least favorable season for Cryptostigmata mites flourishing. The peak of abundance was recorded in November. c. Prostigmata mites: The population density of Prostigmata mites was comparatively high during autumn and summer, while winter and spring seemed to be less suitable for the Prostigmata mite activity. d. Astigmata mites (Acaridae and Histiostomatidae): The Astigmata mites at the citrus orchard sheds increased during winter followed by autumn, then spring followed by summer. On the other side, the Acarididia mites attained their peak during November and December. 3. Relationship between Prostigmata and Mesostigmata mites at the citrus orchards: The density of the Mesostigmata species was increased during autumn and spring seasons, while winter and summer were inconvenient for this group of mites. The opposite was observed in the case of the Prostigmata mites. This may be due mainly to mite behavior and the dependence of the Mesostigmata mites upon Prostigmata individuals as a source of food. The statistical analysis of data revealed the presence of significant positive correlation between the population density of Mesostigmata versus Prostigmata (r = +0.31858*) and higly significant with positive correlation with Astigmata (r= +0.61523**). Practical Application and Recommendations: 1. Research on the taxonomy, morphology and ecology of the citrus mites is promising, especialy in Egypt, as compared with other groups of mites. However, the considerable numbers of species and various morphological differences require more intensive and comprehensive research. Therefore, the present course of investigation intended to give a morphological and taxonomical treatise as apart from the ecological research, this makes the identification of the species pertaining to this group easier, especially the use of the identification keys, based on the morphological characteristics of the adult female and male. 2. Biological control has great potential as a tactic for regulating pest populations in integrated pest management programs (IPM) in citrus orchards. Therefore, it is important to survey predacious mites associated with the citrus spider mites in Egypt and study their role as biocontrol agents in order to minimize the use of pesticides.3. Continuous monitoring of field crops as invasive/secondary pests may appear (e.g., Polyphagotarsonemus latus). 4. More surveys are needed in searching for more predatory species. 5. Cooperation with plant virologists to study the status of (CiLV) transmitted with the flat mite, Brevipalpus phoenicis. 6. Testing the predation ability of the commonly reported predatory species (lab. studies and/or field releases). 7. Laboratory mass rearing of predatory mites reported.