An unusual song-pattern in the Chorthippus mollis group (Orthoptera: Acrididae): local variant or hybrid population?

Summary

Published accounts of geographical variation in the songs of Orthoptera are briefly reviewed. An unusual song-pattern produced by an isolated alpine population of a grasshopper belonging to the Chorthippus mollis group is described and illustrated with oscillograms. Both the song and morphological characters of this population are compared with those of typical C. mollis and C. biguttulus. The status of the population is discussed and it is concluded that the balance of evidence favours the hypothesis that it is a hybrid population resulting from a cross between these two species.     

Attributes associated with probability of infestation by the pi?on ips, Ips confusus (Coleoptera: Scolytidae), in pi?on pine, Pinus edulis

We examined attributes of pi?on pine ( Pinus edulis ) associated with the probability of infestation by pi?on ips ( Ips confuses ) in an outbreak in the Coconino National Forest, Arizona. We used data collected from 87 plots, 59 infested and 28 uninfested, and a logistic regression approach to estimate the probability of infestation based on plot and tree-level attributes. Pi?on pine stand density index was a good predictor of the likelihood of infestation by pi?on ips at the plot level, and a cross-validation analysis confirmed that the model correctly classified 82% of the cases. Diameter at root collar and pi?on dwarf mistletoe infestation level were good predictors of individual tree infestation, and a cross-validation analysis indicated that the model correctly classified 72% of the cases. Results suggest that the occurrence of pi?on ips infestations may be related to stress factors associated with increased stocking and pi?on dwarf mistletoe infestations.