RECORDS OF SOME COLLEMBOLA FROM AGRICULTURAL FIELDS OF NORTH 24-PARGANAS, WEST BENGAL

Collembolans are the commonest soil insects. Being extremely soft bodied and sensitive to various measures adopted in agroecosystem, their population and diversities are depleted. Particularly mechanical abrasive action involved in ploughing, application of chemical fertilizers, pesticides, herbicidal chemicals, etc. impair their growth and development. The species of Collembola, particularly the hyperedaphic and hemiedaphic ones, that occur in agroecosystem from Barrackpore, North 24-Parganas, West Bengal, indicate their tolerance to such rigors of cultivation. In the present investigation, eleven species of Collembola of which three belonging to suborder Symphypleona and eight to Arthropleona were found to occur predominantly in the studied agroecosystem.


INTRODUCTION
Collembolans are the commonest soil insects.Being extremely soft bodied and sensitive to various measures adopted in agroecosystem, their population and diversities are depleted.Particularly mechanical abrasive action involved in ploughing, application of chemical fertilizers, pesticides, herbicidal chemicals, etc. impair their growth and development.The species of Collembola, particularly the hyperedaphic and hemiedaphic ones, that occur in agroecosystem from Barrackpore, North 24-Parganas, West Bengal, indicate their tolerance to such rigors of cultivation.
In the present investigation, eleven species of Collembola of which three belonging to suborder Symphypleona and eight to Arthropleona were found to occur predominantly in the studied agroecosystem.
The most abundant and ubiquitous were Isotomurus balteatus (Reuter), Cryptopygus thermophilus (Axelson), Lepidocyrtus (Lepidocyrtus) sp., Cyphoderus javanus Borner and Brachystome/la sp.occurring during cultivation of all the three crops while the rest were found to remain restricted to a specific type of crop.

METHODOLOGY
Soil samples, drawn from the field, were extracted through modified Tullgren funnels by using a 60-watt electric lamp for the purpose of dessication.The examples were collected in rectified alcohol and were subsequently mounted on slides for the purpose of identification.
Analysis was made of various species of Collembola, occurring in the agricultural fields of Barrackpore, with reference to their occurrence according to months and specific crop.Choudhuri, et ale (1971aChoudhuri, et ale ( , b, 1972Choudhuri, et ale ( ,1975)), Mitra, et ale (1977Mitra, et ale ( , 1981Mitra, et ale ( , 1983aMitra, et ale ( , b, 1986Mitra, et ale ( , 1993) ) and Singh, et al. (1971) contributed to the knowledge of Collembola both from cultivated and uncultivated fields of West Bengal and Uttar Pradesh.

QUALITATIVE ANALYSIS OF COLLEMBOLA WITH REFERENCE TO CROPS
Qualitative analysis of total Collembola, obtained from the experimental plots during cultivation of all the three crops, reveal the presence of eleven species of which six species were crop-specific while others were present during cultivation of all the three crops.Three species, viz., Seira indica, Sminthurus sp. and Isotomodes sp.occurred during cultivation of jute while Sminthurides appen diculatus, Sphaeridia cornuta and Acherontiella sp. were remain associated with paddy only.
An analysis of species, remaining associated with all the three crops, reveals that Isotomurus halteatus reached its population-maxima during wheat cultivation and its lowest population occurred during jute cultivation Cryptopygus thermophilus and Lepidocyrtus (Lepidocyrtus) sp.exhibited their peaks during paddy cultivation and minimum for the former was during wheat cultivation while for the later during jute cultivation and its minimum population occurred during jute cultivation.Brachystomella sp.reached its peak of population during wheat cultivation and its minimum population during paddy cultivation.
Qualitative composition of Collembola, obtained during cultivation of each crop, reveals that eight species of Collembola remain associated with both jute and paddy while five species with wheat.I. halteatus, C. thermophilus, Lepidocyrtus (Lepidocyrtus) sp., C. javanus and Brachystomella sp.occurred during wheat cultivation of which the bulk of the population was of I. halteatus and the least was that of Brachystomella sp.

Table Cont '
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