DNA extraction
DNA was extracted from ethanol-fixed haemolymph and tissue samples using DNeasy Blood and Tissue Kit (Qiagen). Haemocyte pellet was obtained by spinning the cells down with 1400 × g speed for 10 min. After lysis of tissues, P3 Buffer (Qiagen) was added to precipitate out polysaccharides that inhibit PCR reactions. Further extraction was performed in accordance with the protocol provided by manufacturer.