Patterns of relationship between certain leafhoppers and plants. i. responses to plants

Differences in the establishment of the leafhoppers Empoasca devastans and E. kerri motti on different plants are determined by an interaction of the following chief types of their responses in six main stages: (1) Orientation, (2) Feeding, (3) Metabolic utilization of the ingested food determining its nutritive value, (4) Growth, (5) Survival and egg-production, (6) Oviposition. Both the leafhoppers showed equally high attraction and proboscis response to all the six test plants, namely, Gossypium hirsutum, G. herbaceum, G. arboreum, Solanum melongena, S. tuberosum, and Ricinus communis. The quantity and nutritive value of the food ingested by E. devastans decreased in the order: G. hirsutum, S. melongena, S. tuberosum, G. herbaceum, G. arboreum, and R. communis. The growth, particularly in respect of moulting/metamorphosis to adult, also decreased in the same order except that S. melongena was superior to G. hirsutum. But, the suitability of the plants for adult survival decreased in the order: S. tuberosum, S. melongena, G. hirsutum, G. herbaceum, G. arboreum, R. communis. The egg-production and ovipositional response decreased in the order: S. melongena, G. hirsutum, S. tuberosum, G. herbaceum, G. arboreum, R. communis. The interaction of the above responses would render S. melongena most suitable for the establishment of E. devastans and the suitability of the remaining plants would decrease in the order: G. hirsutum, S. tuberosum, G. herbaceum, and G. arboreum, while R. communis would be completely unsuitable. The quantity and nutritive value of the food ingested by E. kerri motti from R. communis as well as its growth, survival, egg-production and oviposition on this plant were the highest. Therefore, this plant would be most suitable for the insect's establishment. S. tuberosum and G. hirsutum were next to R. communis in respect of the quantity and nutritive value of the food ingested, growth and adult survival, but there was no egg-production nor oviposition. Therefore, these two plants would support the growth of the larvae and survival of the adults, if present, but not reproduction. The remaining plants were completely unsuitable for both egg-production and oviposition, and therefore would not support the insect's establishment.