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Seasonal Changes in the Susceptibility of Crescentia Alata Leaves to the Flea Beetle, Oedionychus SP.

Rockwood, Larry L.
Ecology 1974 v.55 no.1 pp. 142-148
Chrysomelidae, Crescentia alata, adults, defoliation, dry season, herbivores, leaves, physical properties, seasonal variation, survival rate, trees, wet season, Costa Rica
Eight experimental Crescentia alata (Bignoneaceae) trees were hand—defoliated during the middle of the rainy season, 1970, in the Guanacaste Province of Costa Rica. The crop of new leaves produced by these trees was severely attacked and eaten by adult Oedionychus sp. (Coleoptera: Alticidae). Three trees lost 100% of their leaves while leaves on control trees were not eaten. All experimental trees again put out new leaves and were again attacked by the beetles, though not as severely as the first time. Leaves 4 to 6 months old on control trees and within experimental trees showed little if any damage. During the second beetle defoliation 82.1% of new leaves were damaged in some ways whereas only 29.2% of mature leaves on control trees showed damage of any kind. The mean number of undamaged leaves per meter branch on experimental trees was 83.3 as compared to 301.6 undamaged leaves per meter branch on controls. It is concluded that beetles readily eat any new leaves they can find but do not normally eat mature leaves. Adult beetles that survive the dry season probably reproduce at the beginning of the rainy season when there is an abundance of new leaves of C. alata. The survivorship of the new generation of adults may depend upon the quantity of new leaves they can find during the remainder of the rainy season. Seasonal changes in the chemical and physical properties of leaves probably have important effects on their suitability as food to herbivores. As in the case of C. alata and Oedionychus, plant parts may be edible for a short time only, when they are immature or senescing. Thus the abundance of herbivore food in the world may be more apparent than real.