The Castor semi-looper, (Achaea janata), also known as Croton caterpillar, is a Noctuid moth, the caterpillars of which are termed 'semi-loopers' due to their mode of locomotion. It is found from the Indo-Australian tropics and subtropics, extending south to New Zealand and east through the Pacific archipelagoes to Easter Island. It is a major pest of castor throughout the world.
Wingspan is about 60-70mm. Pale reddish brown body. Fore wings with prominent markings, but sometimes almost obsolete. A short sub-basal waved line and an obliquely waved antemedial and excised postmedial lines present. Postmedial lines are often black suffused inside them. A speck found at end of cell. A diffuse rufous band runs beyond the postmedial line, Hind wings black with medial white band. Three large white spots can be seen on outer margin, with whitish cilia. Ventral side grey suffused. Fore wings with an oblique white postmedial band not reaching the costa. Two crenulate medial lines found on each wing.
Eggs are small, spherical with a greenish color. Pupa is whitish-green.
Larva bluish grey in color speckled with blue-black. Head black-striped. Lateral and sub-lateral yellowish bands with intervening blue-grey line. A dorsal black stripe bordered by reddish-white spots between fourth and fifth somites. There is a pair of dorsal red tubercles on anal somite. Spiracles and fore legs are red. Four larval instars completed before pupal stage.
They feed on Excoecaria cochinchinensis (Euphorbiaceae),  castor oil plant (Ricinus communis), both Brassica and Ficus species and many more crops like Arachis hypogaea, Citrus, Corchorus, Dalbergia sissoo, Dodonaea viscosa, Euphorbia hirta, Glycine max, Lagenaria siceraria, Punica granatum, Rosa chinensis, Solanum lycopersicum, Tamarindus indica, Theobroma cacao, Vigna mungo and Ziziphus mauritiana.
Attack and control
As they feed off the castor oil plant they may be extremely poisonous and should be avoided at all costs. Caterpillars damage foliage, results defoliation and reduction of photosynthesis process. They also attack stems and bore into them, and finally whole the plant wilt and die.
Controlling mainly include mechanical, biological and chemical methods. Hand picking of late instars and usage of pheromone traps and light traps to adults are effective. Many parasitoids are used in biological control. Eggs can destroy using Trichogramma evanescens. Microplitis maculipennis are effective against caterpillars. Chalcid species Euplectrus and another a braconid, Rhogas are also used. In chemical control, Quinalphos, Chlorpyrifos, carbaryl, monocrotophos, endosulphan sprays are used. Neem seed kernal extract sprays are used to destroy eggs.
- "Croton caterpillar". Crop Knowledge Master. Retrieved 12 August 2016.
- "Acanthodelta janata (Linnaeus)". ICAR-National Bureau of Agricultural Insect Resources. Retrieved 12 August 2016.
- Hampson G. F. (1892). "The Fauna Of British India Including Ceylon And Burma Moths Vol-ii". Digital Library of India. p. 558. Retrieved 4 July 2016.
- "Castor Oil Semi-Looper moth (Achaea janata)". Australian Wildlife. Retrieved 12 August 2016.
- "castor semilooper (Achaea janata)". Plantwise Technical Factsheet. Retrieved 12 August 2016.
- Leong, T. M., 2010. Final instar caterpillar and metamorphosis of Achaea janata (Linnaeus, 1758) in Singapore (Lepidoptera: Erebidae: Erebinae). Nature in Singapore, 3: 297–30 Archived January 3, 2015, at the Wayback Machine.
- Ronald F.L. Mau and Jayma L. Martin Kessing. "Achaea janata (Linnaeus)". Honolulu, Hawaii: Department of Entomology. Retrieved December 24, 2013.
- "Important Pests of Castor and its Management". Pests of Castor. Retrieved 12 August 2016.
- Species info
- Life cycle of castor semilooper [Achaea janata Linn. and its control]
- Differential oxidative stress responses in castor semilooper, Achaea janata
- Induction of glutathione S-transferase in the castor semilooper, Achaea janata (Lepidoptera, Noctuidae) following fenitrothion treatment
- Calling behaviour and male response to pheromone gland extracts of castor semilooper, Achaea janata
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