Plant substances metabolized insects

The nutritional requirements of insect species exhibiting different feeding habits like scavengers, parasites, predators and phytophagous insects, are similar in a qualitative sense (O. Each insect species needs, however, a particular quantitative composition of nutrients in its diet to complete development ( ). The presence of toxic substances in plants, secondary plant substances as they were formerly called by phytochemists, forms a barrier which phytophagous insects have overcome by specialization. Thus, an insect can tolerate or detoxify the secondary plant substances present in its host plants, while the majority of these substances being present in other plants still acts as toxins (J ). In this way phytophagous insects are adapted to the metabolic qualities of their host plants, i.e. a particular chemical composition of nutrients and secondary plant substances. 

Luckner, M. Expression and Control of Secondary Metabolism. In Encyclopedia of Plant Physiology, New Series, Vol. 8, Secondary Plant Products (E. A. Bell, B. V. Charlwood. eds.), pp. 23-63, Springer, Berlin-Heidelberg-New York 1980 Mothes, K. Secondary plant substances as materials for chemical high quality breeding in higher plants. In Biochemical Interactions between Plants and Insects (J. W. Wallace, R. L. Mansell, eds.), pp. 385-405. Plenum, New York 1976 Zahner, H. What are secondary metabolites Folia Microbiol. 24, 435-443 (1979)... 

An interesting sidelight on the metabolism of pyrrolizidines is that several butterfly and moth larvae that feed on plants containing these alkaloids metabolize them to products that serve the insects as pheromones or defensive substances. Thus the butterfly Idea leuconoe converts alkaloids from Parsonia laevigata to N-oxides [121]. The moth Creatonotos transiens makes its pheromone, R(-)-hydroxydanaidal from7(S)-heliotrine found in its host plant, Senecio jacobaea [122]. 

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