Host Plant Influences on Iridoid Glycoside Sequestration of Generalist and Specialist Caterpillars

The effect of diet on sequestration of iridoid glycosides was examined in larvae of three lepidopteran species. Larvae were reared upon Plantago major, or P. lanceolata, or switched from one to the other in the penultimate instar. Junonia coenia is a specialist on iridoid glycoside-producing plants, whereas the arctiids, Spilosoma congrua and Estigmene acrea, are both polyphagous and eat iridoid-producing plants. All species sequestered iridoids. The specialist J. coenia sequestered from three to seven times the amounts sequestered by the two generalist species. Junonia coenia iridoid glycoside content depended on diet, and they sequestered from 5 to 15% dry weight iridoid glycosides. Estigmene acrea iridoid glycoside sequestration was relatively low, around 2% dry weight and did not vary with diet. Spilosoma congrua sequestration varied with diet and ranged from approximately 3 to 6% dry weight.