566 IJSR - INTERNATIONAL JOURNAL OF SCIENTIFIC RESEARCH Volume : 2 | Issue : 12 | December 2013 • ISSN No 2277 - 8179 Research Paper Zoology Archita Barua Tocklai Experimental Station, Department of Entomology TRA, Jorhat, Assam-785008 Dr.Azariah Babu Tea Research Association, North Bengal Regional R&D Centre,Nagrakata,West Bengal Dr. Ratul Ch Rajkhowa Cotton College, Department of Zoology, Guwahati, Assam ABSTRACT A survey was carried out to find out the natural enemies of red spider mite in the tea gardens of Jorhat region of Assam. During the survey, a new predatory beetle was recorded and has been identified as Stethorus aptus (Kapur). Life cycle parameters such as incubation period, duration of development, longevity, fecundity of S. aptus was carried out under laboratory condition. The incubation period of the egg ranged from 8 to 10 days and larval developmental period varies from 2 to 4 days. The total development period from egg to adult was complete in 28 to 30 days. The longevity of the female is more than the male and a mature female laid minimum 4 and maximum 12 eggs/day. Study on life cycle parameters of Stethorus aptus (Kapur) (Coleoptera: Coccinellidae): A new predator of tea Red spider mite Oligonychus coffeae (Nietner) (Tetranychidae) KEYWORDS : Red spider mite, Predator, Stethorus aptus, life cycle. INTRODUCTION Tea [Camellia sinensis ( L.) O. Kuntze] is an evergreen perennial plantation crop that plays a major role in the economy of several developing countries. A number of arthropod species survive in the tea ecosystem as it provides suitable habitat and continuous supply of food to them. More than one thousand species of ar- thropod have been documented from tea ecosystem worldwide (Murleedharan, 2001) and about 3% of pests are common glob- ally. The red spider mite, Oligonychus coffeae Nietner (Acarina: Tetranychidae), is considered as one of the serious pest of tea in most of the tea producing countries. For the successful manage- ment of red spider mite, synthetic pesticides are widely used. However, tea being an economically important export commod- ity, the production of tea has to be in compliance with the inter- national regulations on pesticide residues. These issues neces- sitate the development of alternative pest control strategies for rsm management. Biological control is one of the oldest pest management strate- gies that plays a vital role in the control of many tea pests be- low economic injury level. Among them, ladybird beetles gain considerable significance in biological control in several agro ecosystems. The predatory nature of most of the coccinellid beetles makes them economically important. They have the ca- pacity to search and feed ravenously on larval and adult stages of aphids, mites and other soft bodied arthrospods (Kim-Ky- uchin etal.,2000;Babu and Ananthakrishnan 1993; Ara Begum et al., 2002). In the recent years, introduction of indigenous natural enemies are more favored than exotic predators for effi- cient biocontrol and to reduce undesirable ecological problems. (Brader, 1980). In this regard,the predacious ladybird beetles are widely used in biocontrol as majority of them feed on dif- ferent tea pests (Muraleedharan et al. 2001).This coccinellid beetle Stethorus aptus (Kapur) has been newly recorded in the tea growing areas of north east region (Babu, 2012) which was earlier reported as a predator of Panonychus citri of citrus plant in China. (Li et al. 1990). Therefore the biological study on S ap- tus in tea ecosystem is very important in order to evaluate their potential against tea red spider mite. Materials and Methods Stock culture of Stethorus aptus and red spider mite To maintain the stock culture of Stethorus aptus and Oligonychus coffeae in the laboratory, different stages of both the predator and prey were collected from the tea fields of Tocklai Experi- mental Station. The culture was kept at 23+1 0 C and RH 90+5 in the laboratory by following the method of Perumalsamy et.al., 2010. The field collected red spider mites were then shifted to fresh mature tea leaves kept in large plastic trays. The leaves were placed on moist cotton pads to retain their freshness and used as stock culture for the experiment. To have the mass cul- ture of the predatory beetle, various stages of field collected S.aptus were reared in small containers and provided with enor- mous number of red spider mite (larvae and nymphs). The pupa were collected from the container and kept for adult emergence. Life cycle study Newly emerged beetles were kept in small containers and pro- vided with mite infested leaves for their nourishment. To obtain eggs, five pairs of male and female beetles separated and kept in containers for mating. After 24 hour the male and female beetles were separated and kept individually in container for oviposition. The female laid eggs on the dorsal and ventral sur- face of mite infested leaves. The egg laden leaves were regularly changed and placed on trays for hatching having water soaked cotton at the bottom. The newly hatched larval instars were collected with a fine brush and nurtured by giving mite infested leaves in rearing container. The container was covered with a muslin cloth and the lid of the container was perforated with small needle for proper ventilation. Observations on the lifecycle parameters such as pre-oviposition period, incubation period and duration of development of different stages, fecundity and body size of each stage is recorded. RESULTS AND DISCUSSION The biology of Stethorus aptus was studied during winter sea- son of (December 2012 – January 2013), under laboratory con- ditions at temperature 23+1 0 C and RH 90+5. The description of various stages, morphometric measurements and developmen- tal periods of different stages are presented in Tables1 & 2. Stages Mean ± SD ٭(mm) Length (mm) Width (mm) Egg 0.20+0.02 First instar 0.63±0.10 0.32±0.03 Second instar 1.03±0.12 0.32±0.03 Third instar 1.28+0.12 0.41+0.03 Fourth instar 2.40+0.10 0.88+0.05 Pupa 1.50+0.08 1.09+0.09 Adult Male 1.4 +0.08 1+0.03 Female 1.5+0.03 1.1+0.03 Table 1: Morphometric observations on life stages of Steth- orus aptus