Effects of nutritional composition of the diet and treatment with cyantraniliprole on Argiope bruennichi

We hypothesized that the species richness and relative abundance of microbial endosymbionts of Argiope bruennichi affect and can be affected by differences in protein and lipid content of ingested food and by the treatment with Benevia (cyantraniliprole). Therefore, we provisioned the wasp spider Argiope bruennichi with 1) D. melanogaster on standard diet (100% Nekton), 2) D. melanogaster on protein-rich diet (Nekton : caseine provided at a 2 : 3 ratio), 3) lipid-rich D. melanogaster that were raised on sucrose-rich diet (Nekton : sucrose provided at a 2 : 1 ratio), and 4) starving, which was used as a control. The spiders were allowed to form orb webs, which were analyzed, and the spiders were again fed with the same diet for another 18 weeks. During this follow-up period, we treated some spider individuals treated with the insecticide Benevia (FMC Agro Ceska republika spol. s r.o., Prague, Czech Republic) (12 individuals in group 1, 14 in group 2, nine in group 3, and 14 in group 4). We used the field-relevant dose of Benevia (cyantraniliprole at 100 g/L), diluted it at 3.75 mL L-1, and applied it in an amount equivalent to 200 L ha-1 (i.e., 750 mL of Benevia ha-1). The results were read out at 24 h after the treatment with the insecticide. We analyzed the microbiome of the legs and cephalothorax of the tested spiders.