July 2004. The larvae were found eating leaves of castor plant growing in Guyana. The larvae also caused some irritation on the skin when in contact. Is it a known pest of castor? The interest in castor is because it is reported that extracts from the kennels and possibly the leaves have some bio-effect on insects and or plant pathogens. But alas these larvae were voraciously feeding on the leaves!
It is a cup moth, also called slug or nettle caterpillars belonging to family Limacodidae (Eucleidae, Cochlididae). They are occasional and serious pests on several plants of economic importance such as palms (coconut, oil palm, ornamental palms), tea, coffee, cinchona, castor, etc., in South and Southeast Asia. Those recorded from castor are Parasa lepida (India), Spatulicraspeda castaneoceps (India), Altha nivea (India), Thosea cana (India) and Natada sp. (Thailand). None of the larvae of these look anything close to the posted picture from Guyana.
Natada (some chaged to Darna) spp. occur both in the Old World and the New World. Natada pucara and Natada subpectinata have been reported from Central and South Americas on oil palm. Natada velutina recorded on mango in India, and Natada sp. recorded from castor in Thailand.
Bio-activity of the seeds and other parts of castor
Aside from the seeds, other parts of castor plant has ricinin, an active component, which is a toxic protein. Studies conduted by Chitra et al. (1991) found that 1 and 5% aqueous and petroleum ether leaf extract protects host plants from larvae of spotted leaf beetle (Henosepilachna sp.) and according to Haller & McIndoo (1943); De-ong & Frear (1948), other parts of the plants show toxicity to codling moth and its larvae (Prakash & Rao, 1996).