International Journal of Horticulture, 2017,Vol.7, No.2, 7-19
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3 Materials and Methods
3.1 Plant materials
The egg plant,
S. melongena
, teasel gourd,
M. cochinchinensis
and black nightshade,
S. nigrum
leaves (tender and
mature) were collected randomly from the agricultural field near Chinsurah Rice Research Center, Hooghly
(22°53' N, 88°23' E), West Bengal, India. Leaves were initially rinsed with distilled water and dried by paper
toweling for phytochemical analysis.
3.2 Extraction and phytochemical estimation
The freshly harvested
S. melongena
,
M. cochinchinensis
and
S. nigrum
leaves were dipped in different solvents
for extraction of different primary and secondary chemicals. Finally, the variability of the phytochemicals present
in the three host plant leaves were estimated by various biochemical analysis, such as total carbohydrates
(DuBois et al., 1956), total proteins (Miller, 1959), total lipids (Folch et al., 1957), total amino acids (Moore and
Stein, 1948; Roy et al., 2013), moisture(Banerjee and Haque, 1984; Roy and Barik, 2012), total phenols (Bray and
Thorpe, 1953; Roy and Barik, 2012), total flavonoids (Zhishen et al., 1999), tannin (Trease and Evans, 1983),
saponin (Trease and Evans, 1983), phytate (Reddy and Love, 1999), alkanes (Roy and Barik, 2012; Roy et al.,
2012a), fatty acids (Roy et al., 2012b; Roy et al.,2013; Roy and Barik, 2014). Each biochemical analysis was
repeated for three times and expressed in dry weight basis.
3.3 Insect rearing
The insects used in this study were collected by sweep netting from the respective host plants. The insects were
maintained separately in 1 l glass jars, containing respective host leaves, and covered with fine-mesh nylon nets at
27 ±1°C temperatures, 65 ±10% relative humidity, and a 12L: 12D photoperiod in a BOD incubator. The F2
E.
vigintioctopunctata
were used for oviposition separately indifferent sterilized glass jars. Fresh leaves were given
daily by replacing the previous one until eggs were laid by the test insects, and the eggs with each host-plant
leaves were placed in new sterilized glass jars separately. To maintain natural condition of leaves, a moist piece of
cotton was placed around the cut ends of leaf bearing twigs followed by wrapping with aluminum foil to prevent
moisture loss. To study their life table parameters, the eggs were separated and checked daily until all eggs either
hatched or collapsed, and the numbers of daily emerged larvae along with their survival and developmental time
were recorded by daily monitoring. The larvae and adults were reared in sterilized glass jars containing 20
individuals on each kind of host leaves for study their feeding dynamics with five replicates for each host plants.
Thus, the feeding dynamics along with different life table parameters of
E. vigintioctopunctata
were determined
by a single generation with three cohorts for each kind of host leaves.
3.4 Food utilization
The weight gain of insects, the weight of food consumed and the weight of faeces produced were determined in a
monopan microbalance (±0.001 mg). Third generation larvae of approximately same size were selected and
weighed initially and were reared separately into separate sterilized glass jars. They were allowed to feeding on
weighed quantity of three host leaves for 24 h and were reweighed. The fresh weight gain during the period of
study was estimated by determining the differences in weight of larvae or adults. The quantity of the food
consumed was estimated by determining the difference between the dry weight of diet remaining at the end of
each experiment and total dry weight of diet initially provided. All the values were expressed on dry weight
basis through dry conversion values as described by Roy and Barik (2012 and 2013) and Roy (2014). Twenty
individuals were used in each type of host leaves for each instars and adults with five replicates.
3.5 Food utilization indices
Food utilization indices (on dry weight basis) were calculated by the formulas of Waldbauer (1968) with slight
modifications (Thangavelu and Phulon, 1983; Sétamou et al., 1999; Xue et al., 2010; Roy and Barik, 2012; Roy
and Barik, 2013; Roy, 2014) to assess the feeding efficiencies of
E. vigintioctopunctata
as follows:
Growth rate (GR) = P/Q
Consumption rate (CR) = R/Q
Relative growth rate (RGR) = P/QS
Consumption index (CI) = R/QS
Egestion rate (ER) = T/QS
