Biology, ecology and demography of the tropical treehopper Ennya maculicornis (Hemiptera: Membracidae): relationships between female fitness, maternal care and oviposition sites

1. Treehoppers (Hemiptera: Membracidae) exhibit a wide range of social behaviours related to maternal care and nymphal aggregation. Maternal care represents an investment in terms of time and energy leading to trade-offs which bear a strong relationship with parity and can thus affect population dynamics. These trade-offs can be modulated by biotic and abiotic features of the oviposition site. 2. Preliminary observations on Ennya maculicornis (Membracidae: Similinae: Polyglyptini) show that females generally lay a single egg mass, and occasionally two or three egg masses, and that maternal care is a plastic trait because some females abandoned their egg mass before it hatched while other females remained with their offspring after egg hatching. These features make this species an interesting model to study the relationship between female fitness, maternal care and ecological factors such as oviposition site. 3. The biology and natural history of E. maculicornis are described and the relationships in question analysed using demographic parameters estimated by matrix models. Ennya maculicornis showed sexual dimorphism and a longer developmental period than other species of the same tribe. Females exhibited maternal care that increased offspring survival, and preferred mature over young host leaves for oviposition. Finite rate of increase (λ) values were lower than 1, suggesting a tendency towards population decrease. 4. The results represent the first detailed description of the life history and ecology for a species of this genus. Additionally, new hypotheses for treehopper sexual dimorphism, oviposition site choice and the ecological effects on population dynamics are proposed.