~ 206 ~ Journal of Entomology and Zoology Studies 2017; 5(1): 206-208 E-ISSN: 2320-7078 P-ISSN: 2349-6800 JEZS 2017; 5(1): 206-208 © 2017 JEZS Received: 01-11-2016 Accepted: 02-12-2016 S Sambathkumar Department of Agricultural Entomology, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India C Durairaj Department of Agricultural Entomology, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India S Mohankumar Department of Plant Biotechnology, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India N Ganapathy Department of Cotton, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India Correspondence S Sambathkumar Department of Agricultural Entomology, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India Studies on sex ratio of castor shoot and capsule borer, Conogethes punctiferalis Guenee (Lepidopteara: Crambidae) in Castor S Sambathkumar, C Durairaj, S Mohankumar and N Ganapathy Abstract The castor shoot and capsule borer, Conogethes punctiferalis (Guenee) is an important and one of the most devastating pests of castor. The sex ratio of C. punctiferalis adults was compared for two years (2011 and 2012) on castor. The sex ratio (♂: ♀) was female- biased during both years and it was 1.0:1.92 and 1.0:1.41 respectively. The chi-square test for heterogeneity in sex ratio, showed non-significant departure from 1.0: 1.0 ratio in both years. The paired ‘t’ test also revealed the non-significant difference in the sex factor between two years Keywords: Castor, pest, castor shoot and capsule borer, Conogethes punctiferalis, sex ratio 1. Introduction Castor is indigenous to the South Eastern Mediterranean Basin, Eastern Africa, and India, but is widespread throughout tropical regions and is widely grown as oil seed crop. The seeds with hulls removed contain 35 to 55% oil. The castor shoot and capsule borer, Conogethes punctiferalis (Guenee) is an important and one of the most devastating pests of castor. Apart from castor it causes major constraints in the production of other crops like cardamom and some tropical fruit trees. Castor is mostly grown as rainfed crop and not much emphasis is given for the plant protection activities and farmers relied upon only insecticides for managing the insect pests under irrigated cultivation. Development of effective management strategies for controlling C. punctiferalis will require knowledge of its biological relationships with its host plants. Among these, an important component will be an understanding of host suitability [7] . Sex ratio of insects especially in lepidopterans plays a major role in mating and oviposition. Generally, equal number of male female population in the environment leads to exploitation of the complete potential of insect species for reproduction. Hence, the present study on identifying the existing sex ratio of C. punctiferalis was conducted at Department of Agricultural Entomology, Tamil Nadu Agricultural University, Coimbatore during July to December for two successive years (2011 and 2012) from the field collected populations of castor plants. 2. Material and Methods Larvae of C. punctiferalis infested castor shoots and capsules were collected randomly from castor and were brought to the laboratory and randomly 20 larvae along with capsules and shoots were separated. These were kept in plastic troughs (40 cm dia.), with a layer of filter paper at the bottom to absorb excess moisture from the host. The trough was covered with muslin cloth and secured tightly using rubber band. The culture was maintained at a temperature of 27.9 ± 2.2 O C and relative humidity (RH) of 76.6 ± 9.1 per cent. The troughs were regularly examined for pupation and the pupae from the trough were transferred to adult rearing plastic baskets (22.5 cm dia. and 25 cm height). Ten replications were maintained and each replication comprised of 20 randomly selected pupae from the field collected and laboratory cultured population. After the adult emergence males were identified by the presence of tapering abdomen with black colour at tip and female moths had tubular abdomen with a prominent hole at tip. The sex ratio (♂: ♀) and sex factor relationship were calculated using the formulae, Sex Ratio = Number of female moths / Number of male moths Sex Factor = Number of female moths / Total number of moths