On the use of gut characters to determine the origin of migrating aphids

SUMMARY A survey of plant metabolites recoverable from aphids indicated that amino acids, sugars, and phenolic compounds do not provide criteria for associating aphids with their original host plant. An insoluble polysaccharide accumulates in the crop of aphids fed on members of the family Chenopodiaceae, and distinguishes Myzus persicae alatae reared on chenopods from those reared on other host plants. The polysaccharide causes swelling of the crop in alate and apterous aphids transferred to beet from cabbage and persists in the crops of these aphids after subsequent transfer from beet to non‐chenopod hosts, or in aphids removed from beet and starved to death. Migrants from chenopods can be recognized by the intensely positive periodic acid‐Schiff reaction of the crop contents, and the increased cross‐sectional area of the crop, caused by the accumulation of polysaccharide.