Lipids

Lipid content was determined with the sulfophosphovanillin (PV) reaction according to Park et al. (2016). Its high reliability was proved by Williams et al. (2011). As a calibration standard, we used a mix of 1 mg ml⁻¹ tripalmitin (C₅₁H₉₈O₆) 41%, 1 mg ml⁻¹ triolein (C₅₇H₁₀₄O₆) 36%, and 1 mg ml⁻¹ trilinolenin 23% (C₅₇H₉₈O₆) in n-hexane (C₆H₁₄) (Williams et al. 2011). For lipid extraction, we used a mixture of hexane and isopropanol (3:2) according to Guckert et al. (1988), Guckert and White (1988) and Palmquist and Jenkins (2003), instead of chloroform and methanol (Lee 2019; Lorenz 2003). Hexane and isopropanol extract a smaller portion of polar lipids, and this way of phospholipids in cell membranes, in comparison to chloroform and methanol (Guckert et al. 1988; Guckert and White 1988; Palmquist and Jenkins 2003), and this way improve determination of storage lipids. The fine-grained reaction powder produced with the Retsch mill promised an accurate extraction of storage lipids.

The wasp samples and a lipid standard in concentrations of 0, 10, 20, 30, and 40 µg ml⁻¹ were measured in disposable PMMA cuvettes in a photometer at 530 nm wavelength, with air as a reference.