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N. Senthilkumar , K. P. Sanjayan

Abstract

Development of Conocephalus maculatus under controlled environmental conditions was studied. In order to test whether the development of C. maculatus is influenced by environmental factors, it was bred in the laboratory under simulated environmental conditions. Water/moisture had an influence on embryonic development of C. maculatus as no eggs developed without water. No hatching occurred, when the eggs were incubated deprived of water for varied periods from 50 days to 12 months and then transferred to moist conditions. Results from this study revealed that C. maculatus does not sustain in drought conditions and does not undergo any egg diapause. They require constant access to water for the development till hatching. At controlled temperature of 24°C and 35°C, eggs hatched in 21-37 and 14-21 days respectively. At temperature fluctuating between 20°C to 30°C (Mean 28.6±1.7°C) the incubation period ranges between 16-26 days. It is also indicated that the embryonic developmental period is inversely proportional to increase in temperature. Both males and females pass through a 6 nymphal instar life cycle, with an average embryonic developmental period of 43.5±7.4 (range between 39-52 days) days. The duration of post-embryonic development is short (male 27-31 days; female 32-40days) in high temperature (35°C), but longer in low temperature of 25°C (male 40-49 days; female 48-55 days). From this study it is revealed that change in climatic factors will lead to change in growth and development of C. maculatus and it may be considered as an indicator species on climate change.

Keywords

Conocephalus maculatus, Development Stages, Effect of Climate Change

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N. Senthilkumar , A. Karthikeyan , K. P. Sanjayan , V. Mahalingam , M. C. Muralirangan

Abstract

From a global perspective the Tettigoniids or the Long-horned grasshoppers, appear to be a lesser known group of orthopteroid insects, probably because of the difficulties in sampling, laboratory rearing, and also because of its behavioural and ecological uniqueness. Available information on the bioecological characteristics of tettigoniids around the world is very meager. Moreover, no record is available on the biology of Tettigoniidae of Indian subcontinent. The paper presents the mating and ovipositional behaviour of tettigoniid species Himertula vidhyavathiae Ingrisch and Muralirangan, 2003.

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N. Senthilkumar , K. P. Sanjayan

Abstract

Population dynamics and life tables of Conocephalus maculatus were studied by field census data and laboratory rearing. Five differents localities, representing four habitat types such as forestland (Guindy Reserve Forest), agricultural crop field (Kanchipuram), grasslands (Nungambakkam and Kodambakkam) and wasteland (Chenglepet) were selected as study sites. Adults as well as nymphs were recorded throughout the year in all habitats except at Chenglepet (wasteland) where they were observed only during rainy months from September to November. In general, adult populations showed a slightly decreasing trend in abundance from January to June each year, with the population building up from August and attaining a peak in October. More or less similar trend was observed in all the three years of study. Laboratory breeding was done at a mean temperature of 23°C and a relative humidity of 60% and baby corn (an immature flowering part of Zea mays) as food material. Pieces of Panicum maximum were provided for oviposition. Life tables based on age specific survival and fecundity of mated females, were constructed following the standard procedure. The results from the laboratory observations revealed that 49% mortality was prevalent at the egg stage itself. Survival of C.maculatus decreased with increase in the age. The total generation mortality in laboratory studies is less when compared to the wild population because in the laboratory conditions they are devoid of natural enemies and are not affected by extreme weather conditions. The proportion of female births obtained in the next generation was very low. This is because of the high mortality in the early nymphal stages. The net reproductive rate for the next generation was lowered considerably. In sum this study indicates that the temperature and rainfall play a vital role in the population dynamics of C.maculatus. The differences in the population dynamics of C. maculatus in different habitats may be due to their local physical environment including availability of hosts.

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D. Suresh Chand ¹, S. Albert ², K. P. Sanjayan ²

Affiliations
1 Zoological Survey of India, M-Block, New Alipore, Kolkata-700 053, IN
2 G.S. Gill Research Institute, Guru Nanak College, Velachery, Chennai 600 042, IN

Abstract

The plant community structure of the Vandalore Reserve Forest (Tamil Nadu) which represents a natural scrub-jungle ecosystem, is described in terms of the dispersal and distribution patterns of some of the plant species that are relatively common in the habitat. The generalization that the tropical species are relatively uniformly dispersed did not hold. The six plant species that were selected either randomly distributed or clumped in dispersion. Atalantia tnonophylla which was clumped in dispersion had more abundance value, importance index, and density in the forest, when compared to the other five plant species. The food preference of Diabotocaiantops pingiiis (Walker) to the selected six plant species through a 'no-choice' experiment showed that it rejected Pavetta indica and Flacoiirtia indica. The population analysis of D. pinguis by selecting 25 quadrats, suggested that the insect was found to be present in 21 quadrats.

Keywords

Plant Community Structure, Dispersion, Importance Value, Diabolocatantops Pinguis, Food Preference.

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M. Prabakaran ¹, S. Sithanantham ², K. P. Sanjayan ¹, R. Krishna Mohan ³, S. Parimalarangan ⁴, E. Surendra Naidu ⁴

Affiliations
1 Guru Nanak College, Department of Advanced Zoology & Biotechnology, Velachery Main Road, Chennai-600 042, Tamil Nadu, IN
2 Sun Agro Biotech Research Centre (SABRC), 3/1798, Main Road, Madanandapuram, Chennai 600125, Tamil Nadu, IN
3 Natems Sugars Private limited, Nindra Cross, Koppedu-517587, Chittoor Dist., Andhra Pradesh
4 Natems Sugars Private limited, Nindra Cross, Koppedu-517587, Chittoor Dist., Andhra Pradesh, IN

Abstract

Large area study on the impact of six versus ten releases of the biocontrol agent, Trichogramma chilonis, besides large plot assessment of ten releases with and without mass trapping (by pheromone traps) for eco-safe management of the sugarcane internode borer (INB) - Chilo sacchariphagus indicus Kapur were undertaken in Natems Sugar factory area, Koppedu Taluk, Chittoor District, Andhra Pradesh, South India. In 2017-18, a large contiguous sugarcane crop area of 400 hectares received six releases of T. chilonis (as Tricho cards @ 5cc.ha/release) in alternate weeks during 5-7 months age of crop, followed by four additional releases during 8-9 months age (totalling ten releases) in 40 hectares area, besides assigning a no release block of 40 hectares in adjacent area. Harvest-time sampling in each treatment block showed that the INB distribution (per cent canes infested) was 80 % in control (no release) block, while it was 42 and 27 %, respectively, for six and ten releases. The INB intensity (per cent internodes infested) was also more (6.2 %) in control block whereas it was only 3.2 % and 1.5 %, in the two respective release regimes. Based on these results the cost-effectiveness of both the regimes was ascertained. In 2018-19, the impact of ten releases of T. chilonis (@5cc/hectare /release) versus same regime plus mass trapping (@25 pheromone traps/ha) was compared in large plots (each of 2.0 ha) along with an untreated control plot. Harvest-time samples showed that INB distribution was 70.3% in control block, compared to 48.3% in Trichogramma release block versus 19.8% in block combining Trichogramma and mass trapping. The respective INB intensity was 6.04 %, 4.04 % and 2.17 % while the estimated cane yields were 81.0, 86.2 and 92.5 tons/ha, respectively. The cost: benefit ratios for Trichogramma release with and without mass trapping were comparable, so confirming that both are cost-effective alternatives to chemical insecticide use in sugarcane agro-ecosystems.

Keywords

Chilo sacchariphagus indicus, Internode Borer, Mass Trapping, Sugarcane, Trichogramma Releases.

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