Oxalic acid as a larval feeding stimulant for the pale grass blue butterfly Zizeeria maha (Lepidoptera: Lycaenidae)

Larvae of the pale grass blue butterfly, Zizeeria maha (Kollar) (Lepidoptera: Lycaenidae), feed exclusively on Oxalis corniculata L. (Oxalidales: Oxalidaceae), which accumulates oxalic acid as with other Oxalidaceae species. Larvae were stimulated to feed on artificial diets containing a crude methanolic extract from host plant leaves. Fractionations and bioassays revealed that the strong feeding activity was found in the water layer, from which oxalic acid was detected as a major compound. Removal of oxalic acid as calcium oxalate precipitates by addition of calcium chloride into the water layer resulted in a significant decrease in feeding activity on the filtrate. Re-addition of oxalic acid to the filtrate recovered the feeding activity. The addition of 260 μmol oxalic acid, corresponding to 1 g fresh leaves of Oxalis, to 1 g of artificial diet significantly stimulated feeding compared with the intact artificial diet. Therefore, oxalic acid was concluded to be a major feeding stimulant for Zizeeria maha larvae