Pakistan J. Zool., vol. 44 (3), pp. 685-690, 2012. Impact of Ecological Conditions on Biology of Cotton Mealy Bug, Phenacoccus solenopsis (Hemiptera: Pseudococcidae) in Laboratory Asifa Hameed, 1 Muhammad Asif Aziz 2 * and Ghulam Mustafa Aheer 3 1 Cotton Research Station, Multan. 2 Department of Entomology, PMAS-Arid Agriculture University, Murree Road, Rawalpindi 3 Entomological Research Institute, Faisalabad Abstract.- Effect of temperature and relative humidity on the life history of the cotton mealy bug Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) was investigated in the laboratory. P. solenopsis was able to complete its life cycle at 20, 25, 30 and 35±1°C and 70, 65, 60 and 40±5% RH, respectively. Egg hatching period decreased from 32±0.22 to 0.57±0.15 hours from 20 to 40°C. But at 40°C, the male specimens were unable to pupate and the female specimens despite comparatively very short life span were unable to produce eggs. The highest fecundity was observed at 20°C with each female producing an average of 232.65±2.19 eggs. Development time from egg to adult was the longest for male at 20°C. Increasing temperature and decreasing relative humidity had profound effect on the longevity of the females whereas longevity of males was less affected. Ability of the P. solenopsis to develop and reproduce successfully at 20 to 35±1°C and 70 to 40±5% RH suggests that the pest can develop and build up its populations in different ecological zones within this temperature range. Key words: Development, relative humidity, Phenacoccus solenopsis, cotton mealy bug. INTRODUCTION Cotton, Gossipium hirsutum (Genn), is an important cash, fiber and fodder crop in Sub- continent. Its production is facing a steady decline from 2.194 million tons in 2005 to 2.09 million tons in 2009 in Pakistan due to incidence of sucking pest complex, high cost of fertilizer and pesticides (Dutt, 2007). In 2005, a new menace, cotton mealybug, Phennacoccus solonepsis (Tinsley) appeared in Sindh (Sanghar, Mir pur Khas and Tando Allahyar district) and Punjab (Multan, Vehari, and other cotton growing areas of southern Punjab) provinces of Pakistan (Khushk and Bhagromal, 2005). In 2006, it appeared in Gujrat in India (Saini et al., 2009; Hanchinal et al., 2009; Nagarare, 2009). The pest feeds on more than 154 plants belonging to six different families (Arif et al., 2009). Damage to host crop is due to sucking of twigs and leaves. Sooty mould appears on the twisted twigs and leaves due to which young plants die and elder plants are weakened. Its damage in Punjab started from the hot regions like Vehari and Multan which might be due to the fact that hot weather and lack of rainfall _____________________________ * Corresponding author: aisfaziz@uaar.edu.pk 0030-9923/2012/0003-0685 $ 8.00/0 Copyright 2012 Zoological Society of Pakistan. encourages its development. In India Dhawan et al. (2009) reported positive correlation between increase in temperature whilst negative correlation between rainfall and population of pest. The present study is planned to observe the effect of temperature and relative humidity in the laboratory on biology of cotton mealy bug so that the farmer can take proper management actions against this pest keeping in view the ecological conditions. MATERIALS AND METHODS Experimental conditions The cotton mealy bug specimens were collected from different host plants from Ayub Agricultural Research Institute, Faisalabad, Pakistan during 2007-2008. Plant twigs (15 cm length) containing cotton mealy bugs, were cut with plant cutter and placed in cool box to brought into the laboratory. The adult female cotton mealy bugs were separated for further rearing. The experiments were conducted in the controlled growth chamber maintained at five constant temperatures (20°C, 25°C, 30°C, 35°C and 40°C) with decrease in relative humidity (70, 65, 60, 40) and a light and dark period of 14:10 (L:D) h. Thirty newly hatched nymphs were reared in rearing cells separately at each temperature treatment. But the sample size became different with