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United States Department of Agriculture

Agricultural Research Service

Title: The Relationship Between Density-Dependent Aposematism and Density-Dependent Gregariousness in Palatable and Unpalatable Schistocerca Emarginata (=lineata) Grasshopper Populations

Author
item Sword, Gregory

Submitted to: Metaleptea
Publication Type: Abstract Only
Publication Acceptance Date: August 1, 2001
Publication Date: September 15, 2001
Citation: Sword, G.A. 2001. The relationship between density-dependent aposematism and density-dependent gregariousness in palatable and unpalatable schistocerca emarginata (=lineata) grasshopper populations. In: Metaleptea, Special Meeting Issue. International Conference on Orthopteroid Insects, August 19-22, 2001, Montpellier, France. Poster 75, Oral Presentation.

Technical Abstract: Gregariousness and aposematism are commonly associated in insects. At least one locust species, Schistocerca gregaria, exhibits both density- dependent aposematism and density-dependent gregariousness. Gregariousness has been shown to enhance predator neophobia and avoidance learning of aposematic prey suggesting that color and behavioral phase polyphenism may function in unison as an antipredator strategy. Gregariousness has also been thought to promote evolution of aposematism, however, phylogenetic analyses indicate that gregariousness commonly evolved after aposematism. To determine if an association between density-dependent aposematism and density-dependent gregariousness exists in S. emarginata grasshoppers, I investigated the expression of density-dependent gregarious behavior in grasshoppers from aposematic and non-aposematic populations. I found no difference in the expression of density-dependent behaviors between the different populations. The behavior of first instars from both population was unaffected by rearing density, while final instars from both popula- tions exhibited an increase in activity but not aggregation under high density rearing conditions. These results suggest that density-dependent gregariousness is not a prerequisite for the evolution of density-depen- dent aposematism.

Last Modified: 10/1/2014