Host-selection behavior of nymphs of Vanduzeea arquata and Enchenopa binotata Discrimination of whole twigs, leaf extracts and sap exudates
1984
Kiss, Agnes
The host-discrimination behavior of two species of phloem-feeding membracid nymphs was examined through pair-wise choice experiments using whole twigs, leaf extracts and sap exudates. Both species have restricted host ranges in the field: Vanduzeea arquata is monophagous, while Enchenopa binotata may best be considered narrowly oligophagous in that it represents a complex of sympatric, reproductively isolated populations each associated with a different species or genus of plants. Nymphs of both species settled preferentially on twigs of their respective host plants but those of V. arquata showed absolute discrimination while those of E. binotata selected the alternative twigs a small percentage of the time. Vanduzeea arquata nymphs also showed a greater sensitivity to plant extracts, as a larger proportion of their responses, both positive and negative, were significant. Leaf extracts of all plants tested discouraged ingestion but not probing, and most nymphs exhibited a positive probing response to the extracts of their respective hosts. Only the sap exudates of the hop-tree (Ptelea trifoliata) inhibited ingestion. Enchenopa binotata nymphs from the population associated with the hop-tree also showed a negative response to these extracts but only at a higher concentration. Water-soluble quaternary alkaloids are the secondary metabolites of the hop-tree most likely to be present in the extracts used in this study and in the phloem sap of the plant. They also occur in the honeydew of nymphs feeding on this species. Because these compounds are known to be cytotoxic, it is likely that hop-tree E. binotata nymphs possess physiological specializations to detoxify or tolerate them.
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