HPLC traces of inducible hemolymph peptides in the pea aphid compared to the rice weevil. Representative traces (solid, red lines) are from insects 18 hours after microbial challenge; traces generated from 18 hour control insects are overlaid (dashed, black lines). Phenylthiourea (PTU) served as an internal standard. Arrows indicate peaks that are significantly upregulated (solid, red arrows) or downregulated (dashed, black arrows). (a) Profile from pea aphids challenged with E. coli, showing no upregulated response. (b) Profile from pea aphids challenged with the fungus A. fumigatus, showing some differential peaks. (c) For comparison, profile from rice weevils (Sitophilus oryzae) challenged with E. coli, showing several differentials peaks at multiple retention times.