Figure 1.

The antimicrobial activity of eggs and haemolymph against Escherichia coli D31 was tested using an agar diffusion assay. (a) The antimicrobial activity of untreated Harmonia axyridis (Ha) eggs, final-instar larvae and beetles increased throughout development, whereas the antimicrobial activity significantly declined in adults injected with buffer (Ha adult CONinj) or bacteria (Ha adult BACinj). (b) In Coccinella septempunctata (Cs), the antibacterial activity in untreated eggs, larvae and adults, as well as beetles injected with buffer alone (Cs adult CONinj) was low compared with that observed in beetles following injection with bacteria (Cs adult BACinj). The antibacterial activity of bacteria injected adult H. axyridis (dark grey) is almost comparable with the activity of bacteria injected C. sepempunctata. The results are mean values ± s.e. calculated from independent experiments (further details and the results of corresponding experiments using M. luteus as an indicator organism are provided in the electronic supplementary material).