Morphometric characteristics
The morphometric characteristics of
Earias vittella (F.) are presented in Table 1, 2 and 3. The egg length ranged from 0.51 to 0.72 mm with a mean of 0.62 ± 0.06 mm, whereas the breadth ranged from 0.43 to 0.55 mm with an average of 0.47±0.04 mm. The measurements observed in the present study were slightly higher than those reported by
Suryawanshi et al., (2001) and
Sheoran et al., (2023), possibly due to variations in host plant varieties and environmental conditions.
Four larval instars were observed during the investigation. A progressive increase in larval length and breadth was noticed with each moult. The first instar larva measured 1.70±0.16 mm in length and 0.31±0.05 mm in breadth, while the fourth instar measured 13.41±1.82 mm and 3.31±0.51 mm, respectively (Table 1). Similar observations were reported by
Kulhari et al., (2024) and
Sheoran et al., (2023). The head capsule width increased progressively from 0.22±0.01 mm in the first instar to 0.84±0.03 mm in the fourth instar (Table 3), thereby confirming Dyar’s rule as previously reported by
Suryawanshi et al., (2001).
The pupal stage measured 11.25±0.94 mm in length and 4.82±0.63 mm in breadth (Table 1; Fig 1). Adult morphometric studies indicated distinct sexual dimorphism, with females being comparatively larger than males (Table 2; Fig 2 and 3). Female adults recorded higher body length (10.90±0.80 mm), wingspan (21.55±0.82 mm) and antennal length (8.07±0.30 mm) than male adults. Similar findings were also reported by
Kumar et al., (2024) and
Sheoran et al., (2023).
Developmental biology
Egg stage
Females laid eggs singly on tender plant parts under laboratory conditions (Fig 4). The incubation period ranged from 1 to 5 days with a mean duration of 3.30±1.26 days. Egg hatchability was recorded as 73.45±4.35 per cent (Table 4). The incubation period observed in the present study is in close agreement with the findings of
Suryawanshi et al., (2001) and
Kumar et al., (2024).
Larval stage
The larva passed through four instars under laboratory conditions (Fig 5). The mean duration of the first, second, third and fourth instars was 2.00±0.86, 1.95±0.81, 1.87±0.82 and 2.81±1.23 days, respectively. The total larval period averaged 8.63±1.89 days (Table 4). The developmental durations recorded in the present study are comparable with those reported by
Dhillon and Sharma (2004);
Sharma et al. (2025) and
Kumar et al. (2024). Minor differences may be attributed to variations in temperature, humidity and host quality.
Pre-pupal and pupal stage
The pre-pupal stage lasted for an average of 1.45±0.50 days. The pupal period ranged from 7 to 9 days with a mean duration of 7.82±0.79 days (Table 4; Fig 1). These observations are in agreement with earlier reports by
Suryawanshi et al. (2001) and
Sheoran et al. (2023). Environmental factors and nutritional conditions may account for minor variations in pupal duration.
Adult stage
Adult males survived for 6 to 14 days with a mean longevity of 10.44±2.70 days, whereas female adults survived for 7 to 16 days with a mean longevity of 11.25±2.60 days (Table 4). The pre-oviposition, oviposition and post-oviposition periods averaged 1.85±0.84, 6.17±1.57 and 4.06±2.05 days, respectively. Average fecundity was 161.5±24.91 eggs per female. Female longevity being higher than male longevity is in agreement with the findings of
Sharma et al., (2025); Kumar et al., (2024) and
Pardeshi et al., (2011).
Total life cycle and sex ratio
The total life cycle ranged from 30-43 days in males and 32-45 days in females (Table 4). The sex ratio (male:female) was recorded as 1:1.04, indicating slight female predominance. Similar sex ratio patterns were also reported in earlier studies on
Earias vittella (F.).
Stage-specific life table
The stage-specific life table of
Earias vittella (F.) is presented in Table 5. The highest apparent mortality was observed during the egg and first instar larval stages. Apparent mortality during the egg stage was 14.00 per cent, while the first instar stage recorded 17.44 per cent mortality. The survival fraction increased progressively from the egg stage to the pupal stage. Similarly, mortality-survival ratio and indispensable mortality values were highest during the early developmental stages. These findings are in accordance with
Naresh et al., (2004) and
Sharma et al., (2025), who also reported greater mortality during the early stages of development.
The k-value analysis showed a gradual reduction in mortality pressure from the egg stage to the pupal stage. The egg and first instar larval stages were identified as the critical stages contributing most to generation mortality.
Age-specific life table
The age-specific life table is presented in Table 6. During the initial age interval (0-5 days), 14 individuals died out of 100, while life expectancy was highest at 4.86 days. Mortality increased during the 6-10 day interval and gradually declined during the later age intervals. No mortality was observed during the 31-40 day interval. Life expectancy gradually decreased from 4.86 to 1.00 day with increasing age.
The survivorship pattern followed a Type III survivorship curve, which is characteristic of insect populations exhibiting high mortality during the early developmental stages. Similar survivorship trends were reported by
Sharma et al., (2025); Suryawanshi et al., (2001) and
Naresh et al., (2004).
K-value analysis
The K-value analysis indicated variation in stage-specific mortality (Table 5). Higher k-values were observed during the egg and first instar larval stages, whereas lower values were recorded during the later developmental stages. The total generation mortality indicated moderate survival under laboratory conditions. Similar observations were reported by
Mohapatra (2007);
Kumar and Saha (2025) and
Andrewartha and Birch (1954).
