PARENT SESSION
Poster Session #37: Invertebrate Ecology.
Thursday, August 9, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

The effects of emergence date on the performance in the grasshopper Sphenarium purpurascens (Orthoptera: Pyrgomorphidae) in Central Mexico .

Camacho -Castillo, Edgar¹, Cano-Santana, Zenón ¹, ¹

ABSTRACT- We investigated effects of emergence date on the survival, development and growth in the five instar nymphs of grasshopper Sphenarium purpurascens. We considered two different dates (early and latest) and examined the response of grasshoppers to a range of plants defined for the phenology of vegetation in the Ecological Reserve El Pedregal de San Angel. Emergence date exerted a significant effect on the development and growth between the early and latest nymphs. The early nymphs developed faster and gained more weight compared with the latest although survivorship did not differ. Phenological shifts in the vegetation would be related to the different performance between early grasshoppers and latest, because we observed changes in the food preference along the season. We propose that early grasshoppers experience best conditions in relation to diet quality and the latest grasshoppers may encounter a wide range of plants, but these plants remains available less time. We considered that S. purpurascens populations experience variation in some life history traits such as emergence date.

KEY WORDS: Life history, emergence date, Sphenarium purpurascens, Orthoptera