Abstract
Entomology Journal publishes original research papers and reviews from any entomological discipline or from directly allied fields in ecology, behavioral biology, physiology, biochemistry, development, genetics, systematics, morphology, evolution, control of insects, arachnids, and general entomology. 
INTRODUCTION
Cotton (Gossypium spp.) )Fam. Malvaceae) is one of the most important crops and widely produced agricultural and industrial crops in the world that grown in more than 100 countries on about 2.5% of the world's arable land, making it one of the most significant in terms of land use after food grains and soybeans (Townsend and Liewellyn, 2007) . The Egyptian cotton, Gossypium barbadense L. is a strategic crop with glorious history in Egypt. It is accounted as main source of Egyptian economy, its impact on the economic development of the country is well established and it is rightly known as the white gold in Egypt.
At least 33 tetranychid mite species (Acari) are pests of cotton varieties (Gossypium spp.) throughout the world, of which the most serious are Tetranychus urticae Koch, T. ludeni Zacher, T. turkestani (Ugarov & Nikolski), T. cinnabarinus (Boisd.) (Leigh, 1985) . The mite, T. urticae feeds on various species of plants and attacks more than 200 host plants belonging to orchard, vegetable, green house and field crops world-wide (van de Vrie et al., 1972; Jeppson et al., 1975; Skorupska, 2004) .
In Egypt, cotton plants are attacked by the spider mite, T. urticae which is considered one of the major pests of cotton plants that causes a huge damage in cotton yields and lowers its category (Zaher, 1984) . It is well recognized that the host plant quality affects the development and survival of plant feeding of its herbivores, by impairing growth, lowering resistance to diseases and reducing fecundity (Price et al., 1980 , Adango et al., 2006 . For optimizing the chemical control of this pest or initiating other types of pest management, a detailed knowledge of mite biology and of the factors affecting population growth is required.
Therefore, the present work aims to study the life history and life table parameters of T. urticae reared on two cotton varieties Giza 86 and Giza 90 at 27 ± 2°C and 60 ± 5% R.H. under laboratory conditions. In addition, the correlation between development of the spider mite and phytochemical contents of tested cotton leaves was investigated.
MATERIALS AND METHODS

Tested cotton varieties:
Two cotton varieties Giza 86 (G. 86) and Giza 90 (G. 90) cultivated in Sharkia and Sohag Governorates, respectively; during season 2016 were used in the study. The information related to the two cotton varieties were provided by the Cotton Research Institute, Agricultural Research Center, Egypt, (Table 1) . Leaf samples of both cotton varieties collected from cotton fields in vegetation stage in paper bags to the laboratory Table 1 . Information related to cotton varieties Giza 86 and Giza 90.
The Spider Mite, T. urticae Rearing Technique:
The original colony of the spider mite, T. urticae was supplied from heavily infested cotton leaves which have got from Zagazig district, Sharkia Governorate, Egypt, during season 2016. It was maintained separately on leaf discs (5 cm in diameter) of cotton varieties G. 86 and G. 90 for rearing the spider mite culture in laboratory conditions at 27±2°C and 60±5% R.H. The discs were put on cotton wool pad in Petri-dishes and supplied with water to maintain the leaf discs fresh and prevent mite escaping.
Experimental Procedures:
Leaf disc technique was used to study the biology of T. urticae. Female mites were released on the abaxial surface of each tested cotton varieties G. 86 and G. 90, which put on cotton bed in Petri-dishes (10 cm in diameter). Ten gravid females of the mite were taken from mite culture and released on leaf discs (3 cm in diameter) of cotton varieties for obtaining sufficient number of eggs. After 24 h, females were removed. Just before female emergency (deutonymph), one male from the main colony were added to each leaf disc to assure mating.
Thirty newly larvae were placed singly on fresh cotton leaf discs (2.5 cm in diameter) for both cotton varieties in Petri-dishes. The duration of different stages of the spider mite on each cotton varieties were recorded. Discs were examined twice daily and all biological aspects were recorded until death of mite individuals.
Phytochemical Analysis Procedures of Tested Cotton Varieties:
Leaf samples of the cotton varieties G. 86 and G. 90 cultivated in 2016 season at Sharkia and Sohag Governorates, respectively, were collected during the vegetation growth period, cleaned, washed with distilled water and left to dry at room temperature in appropriate air flow until the samples drying then leaves were grinded into fine powder. Nitrogen, phosphorus and potassium were estimated according to the methods of Sadasivam and Manickam (1991) , Murphy and Riely (1962) , Amin and El-Halafawy (2001/2002) , respectively. Total carbohydrates and total proteins were also determined as the methods described by Crompton and Birt (1967) , Bradford (1976) , respectively.
Statistical Analysis:
Data were analyzed by one-way analysis of variance (ANOVA) to test the significant difference between mean values and correlation coefficient between certain biological aspects of the spider mite and chemical contents of tested cotton leaves were separated by Duncan's multiple range test (Duncan, 1955) . Life table parameters were estimated using a BASIC computer program of Abou-Setta et al. (1986) for female reared on various tested cotton varieties. This program is based on Birch ' s method (1948) for the calculation of an animal ' s life table. Constructing a life table, using rates of age-specific (Lx), and fecundity (Mx) for each age interval (x) was assessed. The following population growth parameters were determined: the mean generation time (T), gross reproduction rate (GRR) (=ƩMx), the net reproductive rate (Ro), the intrinsic rate of increase (rm), the finite rate of increase (exp rm), and the doubling time (DT). The life tables were prepared from data recorded daily on developmental time (egg to first egg laid), the number of deposited eggs, the fraction of eggs reaching maturity and the survival of females. Interval of one day was chosen as the age classes for constructing the life table.
RESULTS AND DISCUSSION
Obtained data revealed that T. urticae developed through egg, larva, protonymph, deutonymph and adult when reared on cotton varieties G. 86 and G. 90 in laboratory at 27±2°C and 70±5 % R.H. (Table 2) .
Duration of Different Mite Stages on Tested Cotton Varieties:
The egg stage hatched after 3.29, 3.58 days for female, 2.56, and 3.37 days for male when fed on discs of cotton varieties G. 86 and G. 90, respectively (Table 2) . Total immatures lived longer on G. 86 than G. 90 averaged 9.86 and 3.82 days for female and 9.62 and 3.09 days for male, respectively. The same trend was recorded in the case of life cycle averaged 13.15 and 7.40 days for female and 12.18 and 6.46 days for male, on G. 86 and G. 90, respectively.
Influence of Cotton Varieties on Adult Female Longevity and Fecundity of T. urticae:
The pre-oviposition period of T. urticae adult female averaged 1.89 and 0.61 days, when fed on G. 86 and G. 90, respectively. The adult female longevity was longer on G. 86 than G. 90 averaged 16.65 and 12.29 days. The number of deposited eggs per female and daily rate of T. urticae averaged 71 and 3.74 eggs when fed on G. 86, but it averaged 98.63 and 8.02 eggs on G. 90. The life span was longer on G. 86 than G. 90 and lasted 29.80 and 19.66 days, respectively (Table 3) . Table 2 . Duration in days of developmental stages of T. urticae fed on leaves of cotton varieties G. 86 and G. 90 at 27 ± 2°C and 60 ± 5% R.H.
Data expressed as mean ± standard error (S.E.). Values followed by a different letter in the same row are significantly different (p≤ 0.05). Table 3 . Effect of cotton varieties on longevity and fecundity of T. urticae adult female at 27±2°C and 60±5% R.H.
Data expressed as mean ± standard error (S.E.). Values followed by a different letter in the same row are significantly different (p≤ 0.05).
Effect of Cotton Variety on Life Table Parameters for T. urticae:
The presented data in Table ( The obtained data is in agreement with that, the intrinsic rate of natural increase (rm) is a key demographic parameter useful for predicting the population growth potential of an animal under given environmental condition (Birch, 1948) , because (rm) reflects an overall effect on development, reproduction and survival (Southwood and Hendeson, 2000) . 
Relationship between Biological Aspects of T. urticae and Chemical Contents of Tested Cotton Varieties:
Total carbohydrates, total proteins, nitrogen, phosphorus, and potassium were estimated in vegetation growth period of cotton varieties G. 86 and G. 90 during season 2016. As shown in Fig. (1, B-C ) data and statistical analysis cleared that total proteins and nitrogen contents ranged between 25.20 and 4.477 mg/gm dry weight for the significant susceptible cotton variety G. 90 but averaged between 21.07 and 3.753 mg/gm dry weight for the significant tolerant variety G. 86, respectively.
The same trend was recorded in the case of potassium content; its values were 405 and 384 m mol/gm dry wt. for G. 90 and G. 86, respectively (Fig. 1, D) . As for phosphorus content among the cotton variety G. 90 and G. 86 averaged 650.667 and 379.667 µg/gm dry wt. (Fig. 1, E) .
On the contrary, the total carbohydrates content recorded the high content in the significant tolerant variety G. 86 compared to G. 90 averaged 55.333 and 38.967 mg/gm dry weight of cotton leaves, respectively (Fig. 1, A) . 
Correlation between Mite Development and Chemical Contents of Tested Cotton Leaves:
Data in Table ( and some biological aspects of T. urticae. Table ( 6) cleared correlation between chemical contents of cotton leaves of variety Giza 90 and some biological aspects of T. urticae gave positive insignificant correlation between total carbohydrates and life cycle and longevity recorded 0.991 and 0.362 except with total immatures, life span and fecundity recorded negative insignificant correlation gave -0.637, -0.637 and -0.491, respectively; in case of total proteins recorded negative insignificant correlation with total immatures and life span recorded -0.991 and -0.952 except with life cycle, longevity and fecundity recorded 0.819, 0.899 and 0.952, respectively; while in case of nitrogen gave positive insignificant correlation with total immatures, life span and fecundity recorded 0.789, 0.789 and 0.668 except with life cycle and longevity recorded -0.997 and -0.555, respectively; positive significant correlation recorded between phosphorus and total immatures, life cycle and fecundity gave 0.967, 0.967 and 0.997, respectively, and 0.957, 0.957 and 0.891 with potassium, respectively, except with life cycle and longevity which recorded negative insignificant correlation gave (-0.539, -0.998 * ) with phosphorus and (-0.901, -0.817) with potassium, respectively. Table 6 . Correlation coefficient between phytochemical contents of cotton variety Giza 90
Results in
and some biological aspects of T. urticae.
Positive relationship was found between mite infestation and both nitrogen and protein contents in cotton leaves. The same results were obtained by Mead et al. (2010) when they tested different maize varieties against T. urticae. In addition, Ahmed (1994) suggested that resistance of host plants to mite infestation might be attributed to low protein and amino acid contents in leaves, which provided less nutritive diet for the spider mite T. urticae. Hanna et al. (1982) observed a reduction in the duration of pre-ovipostion period and increase in oviposition period as the nitrogen contents increased. In addition, Trindade and Chiavegato (1999) observed that nitrogen and phosphorus deficiency or potassium excess caused reduction in the reproduction rate of T. urticae. Also, Maia and Busoli (1992) stated that the relationship between nitrogen contents and reproduction of T. urticae population by recording a reduction in the duration of pre-ovipostion period and increase in ovipostion period as the nitrogen contents increased. Atwa et al. (1987) stated that the total amounts of protein and potassium in leaves of the host plant did not effect on development of spider mite; on the other hand, amino acids and carbohydrate content were positively correlated with the development and female fecundity of Eutetranychus anneckei Mayer and T. urticae. The correlation between biological aspects of T. urticae and both leaf nitrogen and total protein contents may be explained by Hoffland et al. (2000) who stated that the protein concentration in tomato leaves is positively correlated with nitrogen availability. The obtained results are in agreement with Tulisalo (1972) who reported that fecundity of T. urticae was independent of variations in type and levels of carbohydrates because of different pathways for carbohydrates metabolism exist. In addition, Zaher et al. (1980) recorded insignificant positive correlation between infestation of soybean with T. urticae and leaf nitrogen content. On the contrary, Magouz et al. (2006) and El-Sanady et al. (2008) reported a negative correlation between the population density of moving mite stages and nitrogen contents in soybean leaves. The obtained data are in agreement with Taha et al. (2014) who stated that cotton genotype Giza 90 was the most susceptible to T. urticae infestation during 2010 and 2011 seasons. On the contrary, Wilson (1993) reported that T. urticae populations were unaffected by cotton varieties in Australia.
It is concluded that cotton variety Giza 90 was the suitable one for two-spotted spider mite because of its shorter immature developmental period and higher reproduction and intrinsic rate of natural increase. 
‫البقعتين‬ ‫ذو‬ ‫العنكبوتي‬ ‫للحلم‬ ‫الحياة‬ ‫جدول‬ ‫و‬ ‫تطور‬ ‫علي‬ ‫المصري‬ ‫القطن‬ ‫من‬ ‫صنفين‬ ‫تأثير‬


{'paper_id': '182400711', 'title': 'Effect of Two Egyptian Cotton Varieties on Development and Life Table of the Two-Spotted Spider Mite, Tetranychus urticae Koch (Acari: Tetranychidae) in Relation to Leaf Chemical Contents', 's2_url': 'https://api.semanticscholar.org/CorpusID:182400711', 'source': 'S2ORC'}