Junonia orithya (Linnaeus, 1758)

Banerjee, Debdulal, Singhamahapatra, Aniruddha & Roy, Subhajit, 2023, New larval host plants for three butterfly (Lepidoptera, Papilionoidea) species from Rahr region of West Bengal, India, Journal of Insect Biodiversity and Systematics 9 (1), pp. 67-79 : 69

Junonia orithya (Linnaeus, 1758)

Common name: Blue Pansy ( Fig. 1) ( Table 2)

Biology. On 19 th July 2020, the first author spotted a couple of spherical pale green eggs ( Fig. 1B) beneath the young leaves of a Centranthera tranquebarica plant ( Fig. 1A) at S1 (in a dry grassland on the edge of deciduous forest near Madhaiganj village). The 12 cm high herb was hardly distinguishable amongst the grasses, had it not been for the yellowish flowers, which bloom in the dusk and fall at daytime. Stems of the plant along with leaves were collected. Eggs hatched on 22 nd July 2020 and the egg shell was eaten by the pale yellowish green larva ( Fig. 1C), whose body was covered with many small-dark tubercles. Long dark setae emanated from the tubercles. The caterpillars turn into darker brown ( Fig. 1D) in the successive instars, gradually turning blackish in the 6 th (final) instar. The frons of the head capsule gradually turned into orange in the 4 th instar, from initial black in the first and second instars. The larvae were found to feed exclusively on young leaves, with the younger instars feeding superficially on laminae of young leaves. The younger instars stayed on the underside of the leaves ( Fig. 1C), while the later instars were found on shoots and leaf litter, and often fed at night. Dark brown pupa ( Fig. 1G), pale brown ventrally and in the wing pads, formed on 12 th August 2020. Whitish dorsal bands were present in the pupae near the cremaster and mid-abdomen. An adult male butterfly ( Fig. 1H) eclosed from the pupa on 19 th August 2020. A female adult emerged on the same day from the other collected egg. Both the eggs thus eclosed on 32 nd day, after 7 days of pupation. All the eggs and larvae were observed on flowering individuals of the herb. Once the larva matures and stops feeding, it moves to sides of rocks or larger plants nearby in search of space to pupate. The reared larvae were also found to move away from the host shoot and to pupate on the wall of the plastic container. Pupa, which hangs free by cremaster, is formed always close to the ground. They are known to fly throughout the year in particularly dry and arid regions, such as uncultivated stony fields and roads (Wynter-Blyth, 1957) and are hence more common towards the western region of the Rarh, compared to the more humid fertile Gangetic plains in the east. Adult females are known to lay eggs in concealed positions on young shoots (van Son, 1979)

Behaviour. When alarmed, the initial instars of the larvae have been found to fall down from the small plant into the dense grasses to conceal themselves. Another interesting defensive mechanism of rolling itself into a tight spiral, similar to various millipedes ( Dettner, 2010) and pangolins has been noted. The host plant, a delicate small common medicinal parasitic herb ( Mahendru et al., 2022) measuring within 15cm in height, is normally miscible among the grasses in semiaquatic sandy grasslands ( Singh, 1997) and wastelands on wet laterite soil ( Rao & Kumari, 2002), known to flower between August and October ( Paria & Chattopadhyay, 2005), provides an ideal safety cover for the eggs and larvae. The adult butterfly flies mostly close to the grounds, and is known to camouflage itself by closing the wings. Apart from their larval host plants, the adult females often lay eggs on other plants close to their hosts and on rocks or stony paths nearby.

Distribution. Junonia orithya is distributed through Australia ( Butler, 1875), the Oriental region (south and south-east Asia), Middle-east (west Asia) and Africa (van Son, 1979). Widely distributed throughout India , it is absent only in high altitudinal territories such as Ladakh, and Sikkim ( Kunte et al., 2022). In West Bengal, it is quite common in the western districts of Jhargram, Paschim Medinipur, Purba Medinipur, Purulia, Bankura, Paschim Bardhaman, Birbhum, while it is rarely sighted in the Gangetic plains of Hooghly, Nadia, Kolkata, North and South 24 Parganas ( Kunte et al., 2022).