The Canadian Entomologist (1998) 130, 551-577
D.J. Lactin and D.L. Johnson (1998)
Environmental, physical, and behavioural determinants of body temperature in grasshopper nymphs (Orthoptera : Acrididae)
The Canadian Entomologist 130 (5), 551-577
Abstract: We describe a model which estimates grasshopper body temperature (Tb) by linking energy-flow equations with empirical descriptions of aboveground gradients of air temperature (Ta) and wind speed. The model was tested using restrained grasshopper nymphs; estimated and observed Tb agreed well (r2 > 0.81). At a rangeland site near Lethbridge, Alberta, Canada (49 °42'N, 112 °48'W), we observed 315 free-living grasshoppers. We recorded the shadow each cast on a horizontal surface, then reconstructed their orientation to the sun by geometric analysis. We used the model to estimate their Tb and the range and frequency of possible Tb within their environment. Modelled Tb exceeded Ta, and was generally lower than the modelled maximum possible Tb, but was well correlated with Tb of insects on top of the dense layer of vegetation which pervaded the site. This observation suggests that behaviours which elevate Tb are constrained by environmental barriers. Tb exceeded the value expected if insects were located and oriented randomly within their environment (mean difference = 3.95 °C, SE = 0.115); this is unequivocal evidence for behavioural thermoregulation. Heuristic simulations using temperature-dependent developmental- and feeding-rate equations for Melanoplus sanguinipes (Fabricius) suggest that thermoregulatory behaviour increased these rates by 30-40% compared with those for insects located and oriented randomly within their environment. During this study, population processes were never inhibited by excess heat; therefore any climatic warming at the experimental site will probably accelerate the phenology of these grasshopper species. Effects at other sites may differ; the model can be applied to test this possibility.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Dan L. Johnson
Research topic(s) for pests/diseases/weeds:
environment - cropping system/rotation
general biology - morphology - evolution
Pest and/or beneficial records:
Beneficial | Pest/Disease/Weed | Crop/Product | Country | Quarant.
|
---|---|---|---|---|
Melanoplus sanguinipes | Canada (west) |