Journal of Environmental Biology

Response of multiple generations of semilooper, Achaea

janata feeding on castor to elevated CO₂

M. Srinivasa Rao*, K. Srinivas, M. Vanaja, D. Manimanjari,

C. A. Rama Rao and B. Venkateswarlu

Central Research Institute for Dryland Agriculture, Hyderabad-500 059, India

*Corresponding Author email : msrao@crida.in

 Publication Data

Paper received:

17 February 2012

Revised received:

06 July 2012

Accepted:

08 August 2012

Abstract

The growth, development and consumption of four successive generations of? semilooper, Achaea janata reared on castor (Ricinus communis L.) foliage grown under elevated carbon dioxide (550? and 700 parts per million ) concentrations in open top chambers were estimated at Hyderabad, India. Significantly lower leaf nitrogen, higher carbon, higher relative proportion of carbon to nitrogen (C: N) and higher polyphenols expressed in terms of tannic acid equivalents were observed in castor foliage under elevated CO₂?levels. Significant influence on life history parameters of A. janata viz., longer larval duration, increased larval survival rates and differential pupal weights in successive four generations were observed under elevated over ambient CO₂?levels. The consumption per larva under elevated CO₂?increased from first to fourth generation. An increase in approximate digestibility and relative consumption rate, decreased efficiency of conversion of ingested food and digested food and relative growth rate of the four generations under elevated CO₂?levels was noticed. Potential population increase index was lower for successive generations under both elevated CO₂?over ambient. The present findings indicated that elevated CO₂?levels significantly alter the quality of castor foliage resulting in higher consumption and better assimilation by larvae, slower growth and longer time to pupation besides producing less fecund adults over generations.

Key words

Achaea janata, Castor, Elevated CO₂, Generations, Insect performance indices,

Potential population increase index

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