The fall army worm Spodoptera frugiperda (J. E. Smith) (Noctuidae: Lepidoptera), is a new invasive species in India and known for polyphagous behaviour (Montezano et al., 2018). It is native to the Americas and found in most parts of the Western Hemisphere. Of late, the pest was noticed in West and East Africa. Currently, this pest is damaging crops in over 20 African countries (Goergen et al., 2016; Abrahams et al., 2017; Cock et al., 2017). In Brazil and United States, the pest has been reported to causes 32-60% reduction in yield (Hruska and Glandstone, 1988; Wiseman and Isenhour, 1993; Lima et al., 2010). In India, a quick roving survey at Karnataka suggested that pest can cause the damage ranging from 9 to 62.5% on maize (Ganiger et al., 2018; Shylesha et al., 2018). It has been reported for the first time in Karnataka state, India on maize (Ganiger et al., 2018; Sharanabasappa et al., 2018). Subsequently, it has been reported from other maize growing states viz., Tamil Nadu, Andhra Pradesh, Telangana, Maharashtra, Gujrat and northeastern states (Swamy et al., 2018; Srikanth et al., 2018; Chormule et al., 2019). This pest is occurring in serious proportions, causing significant damage to maize. It is important to know the biology and feeding behaviour of this. The earlier reports on the bionomics on artificial diet include Nagamandla and Uma (2019). In the present study, the bionomics are studied on its natural host maize under laboratory conditions.

The initial culture of S. frugiperda was collected from the maize fields near College of Agriculture, University of Agricultural Sciences, GKVK, Bengaluru, Karnataka. The field collected larvae were reared on maize leaves placed in plastic rearing boxes and fresh maize leaf bits were provided every day till the end of larval stage in laboratory (27±2°C, 60-75%RH, L12:D12 photoperiod). The grown-up larvae were transferred to the cages containing a layer of coco-peat as substrate for pupation. The pupae were collected and placed in an oviposition cage for adult emergence. The moths on emergence were provided with young maize seedlings as substrate for the oviposition and cotton soaked in 10% sugar solution as their food. Ten pairs of adults were maintained separately in ovipositional cages to record the fecundity. Egg masses were collected every day and individual larval rearing (n=25) was continued using maize leaf bits as feeding substrate till pupation. The observations on life stages viz., egg, larva, pupa and adults were recorded daily. The parameters like preoviposition period, oviposition period, post-oviposition period, egg period, larval period (instars-wise), pupal period, adult longevity (Male and Female) and total length of life cycle in days were observed.

Egg: The mated females laid eggs in masses of 80 to 250 on both surfaces of leaves, whorls and at the base of the young seedlings (Fig. 1). Freshly laid egg masses were light green in colour covered with greyish scales. A single gravid female was noticed to lay 3 to 4 egg masses with overall fecundity of 780 to 1200 eggs per female. A mean incubation period of 2.80 days was observed. The observations are similar as reported earlier (Luginbill, 1928; Sparks, 1979; Sharanabasappa et al., 2018). Larva: There were six instars in one life cycle. First instars were greenish in colour with black head and seen in congregation when they hatched (Fig. 2). The second instar larvae were turned to light brownish colour with series of black spots on the body (Fig. 3). Third instar larvae were brown in colour with well-developed head capsule and developing hair like setae all over the body (Fig. 4). Fourth instar larvae were greenish brown with prominent black spots and well-developed cuticular setae all over the body (Fig. 5). Later instars were dark brown with three whitish dorsal lines. Head with well-developed inverted-Y suture was noticed. On eight abdominal segments the black spots were arranged in square manner, but were arranged in trapezoidal manner on remaining abdominal segments (Fig. 6, 7). Larval period was completed on an average of 15.70 days and same was observed to differ depending on the rearing temperature. The similar morphological observations and larval durations were recorded in the earlier reports (Sharanabasappa et al., 2018; Ganiger et al., 2018; Deole and Paul, 2018).

Pupa: Before going for pupation larvae stops feeding. Initially pupae were light green in colour, later turned to dark brown colour with well-developed cremaster at anal end (Fig. 8). The mean pupal period of 10.04 days were recorded. Similar pupal characters with pupal period ranging from 6 to 14 days were recorded (Deole and Paul, 2018; FAO, 2018). Contrarily, varying pupal period of 8.54 to 9.70 days was observed depending on host plant larvae fed (Silva et al., 2017). Adult: The adults of S. frugiperda are varying in their morphology. Male adult moths with greyish brown body, light brown coloured fore wing with whitish triangular patch at apical margin and distinct circular spot at the centre (Fig. 9). Adult female with uniform greyish brown forewing without any distinct markings on wing (Fig. 10). Hind wings of both the sexes were whitish with brown border. The longevity of male adult was 7.90 days with a total length of life cycle 35.05 days. But female adults were survived longer compared to male adults with longevity of 11.20 days and total length of life cycle was 38.30 days. The pre-oviposition, oviposition and post-oviposition periods of 2.95, 3.10 and 4.50 days were observed. The similar observations on adult male and female morphology were made by Ganiger et al. (2018) during their report of occurrence of fall armyworm in Karnataka, India. Adult insect were recorded to have longevity of 2 to 3 weeks (FAO, 2018). Contrarily, Deole and Paul (2018) reported adult longevity of 5 to 7 days, the variations may be attributed to feeding of adult insects with sugar solution, where it enhances longevity of adults.

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