TRENDS IN BIOSCIENCES 6-1, 2013 EDITION

34 Trends in Biosciences 6 (1), 2013
emerged adults were kept in rearing jar and were provided
with aphids as food materials. Fresh food was provided every
day and observations on the mortality, if any, were recorded.
Feeding potential of C. sexmaculata
Fifty or sixty freshly collected aphids for adult
coccinellids and 10 for grubs viz., A. craccivora and Lipaphis
erysimi were placed on fresh and tender mustard and bean
leaves/twigs, respectively. The aphids were then allowed to
settle. Different instars of grubs and adults of coccinellids
starved for 2 hours except first instar grub were released singly
inside each petridish with the help of a fine hair brush. The
daily consumption by instars all of larvae and adult of
coccinellids was calculated. Thereafter, the number of
unconsumed aphids left over in the petridishes were collected
daily and calculated for consumed ones. The actual number
of aphids consumed by grubs/adult was obtained by
subtracting the number of aphids left over from the total number
of aphids supplied every day.
RESULTS AND DISCUSSION
Description of different stages of C. sexmaculata
Egg
Freshly laid eggs were cigar shaped, yellow in colour
with smooth chorion and without any reticulations. The eggs
turned blackish with advancement of age and became
completely black before hatching. The eggs were usually laid
in clusters of 4 to 10 and each cluster consisted of 5 to 25
eggs. Number of eggs laid by an individual female of C.
sexmaculata ranged from 150-210 eggs during her life period.
These findings are supported by the findings of Zala, 1995
and Tank, et al., 2007. The incubation period varied from 2-4
days with an average of 3.00±0.58 days (Table 1), which is in
accordance with the findings of Tank, et al., 2007.
Grub
During the present study, it was observed that the larvae
of C. sexmaculata moulted thrice and thus there were four
instars. Freshly hatched larvae were dark grey in colour with
shining dark head capsule and legs. The first instar larval
period lasted for 2.67±0.33 days (ranged 2-3 days) (Table 1).
Second instar larvae were glistening black in colour with
yellow coloured head capsule and black legs. Development
of white coloured patches on meso and metathorax and also
on fourth and sixth abdominal segments was observed. The
second instar larval period lasted in 2.00±0.58 (ranged 1-3
days) (Table 1).
The freshly moulted third instar larvae were dull black in
colour with yellow head capsule. The colour pattern was more
intensified with additional development of white spots on
mid-dorsal line of other segments except prothorax. The third
instar larval period was lost in 2.67±0.33 (ranged 2-3 days).
Table 1. Developmental period of different stages of C.
sexmaculata
S. No. Stage
Duration (days)
Range Mean*
1 Egg (incubation period) 2-4 3.00±0.58
2 Grub
First instar
Second instar
Third instar
Fourth instar
2-3
1-3
2-3
3-5
2.67±0.33
2.00±0.58
2.67±0.33
4.00±0.58
3. Pre-pupa
Pupa
2-3
4-5
2.67±0.33
4.67±0.33
4 Adult longevity
(a) Female
(b) Male
33-38
29-33
35.33±1.45
30.67±0.88
5 Total period taken from egg
laying to adult emergence
16-26
*Mean of three replications with 10 pairs of adult male and females
Fourth and final instar grubs were deep black in colour, when
freshly moulted but changed to dull black in colour before
pre-pupation. It developed additional rectangular dark grey
spots in a continuous series mid-dorsally on abdominal
segments, whereas the spots on the fourth abdominal segment
were white. The fourth instar larval period was lost in 4.00±0.58
(ranged 3-5 days) (Table 1).
The present investigation revealed that the mean
duration of first, second, third and fourth instars larvae of C.
sexmaculata were 2.67±0.33, 2.00±0.58, 2.67±0.33 and 4.00±0.58
days respectively and the total larval period lasted for 8-14
days. Whereas Tank and Korat, 2007 observed that the mean
duration of first, second, third and fourth larval instars were
1.80±0.50, 1.72±0.46, 1.88±0.53 and 1.96±0.73 respectively and
the total larval period ranged from 5-10 days. More or less
nearest values of duration of different larval instars had been
recorded by Rai, et al., 2003.
Pre-pupa and Pupa
When larva was about to pupate, it turned wood brown
in colour and assumed curved shape and attached itself
posteriorly to the substrate. The pre-pupal period was lost in
2.67±0.33 (ranged 2-3 days) while the pupal period was lost in
4.67±0.33 (ranged 4-5 days) (Table 1). Freshly formed pupae
appered shinning yellow in colour which later on became pale
appering orange yellow in colour. There were symmetrically
orange black spots on each segment. This is in accordance
with the report of Sureja, 1991 and Tank and Korat, 2007
observed pre-pupal and pupal period was 1.72±0.45 and
3.36±0.70 days respectively.
Adult
Freshly emerged adults were soft bodied, yellowish in
colour without any markings which turned shining yellow or
warm buff with black spots which developed gradually. The
adults were small, oval, convex dorsally and flat ventrally.
Abdomen and eyes were light yellow in colour whereas elytra
and pronotum were marked with zigzag markings. Similar