The humidity reactions of oribatid mites
1964 - Volume: 6 Issue: 3 pages: 566-591
effects of humidity
The reactions and behaviour of four indicator species of oribatid mitesto linear and alternative relative humidities at constant temperatures have beenstudied. 2. An arboreal species, Humerobates rostrolamellatus Grandjean inatially chose a dry humidity; the humidity reaction was reversed to a moist one after 4-5 days. Belba geniculosa Oudms., collected from oak-litter, had an initial moist reaction. Platynothrus peltifer (Koch), found in litter and bog moss, had a similar reaction. A species found in permanently damp sphagnum, Fuscozetes fuscipes (Koch), showed no marked responses to humidity gradients. 3. The higher the temperature, the greater the choice for the higher humidity. 4. H. rostrolamellatus changed its initial dry reaction to a moist one after 5 days desiccation at 15° C when one-third of its original body-weight was lost. The initial moist reaction of B. geniculosa was much intensifi.ed after only 6 hours desiccation, when merely one-twenty fi.fth of its body-fluids were lost. 5. B. geniculosa showed a stronger initial moist reaction when starved for one week. This behaviour persisted for II weeks. 6. The intensity of the dry reaction of H. rostrolamellatus was correlated with the steepness of the difference in humidity rather than the position of the humidity in the humidity range. With B. geniculosa and P . peltifer the position of the higher humidity in the humidity range was more important than humidity differences in the low end of the humidity scale. F. fuscipes again showed little response. 7. The higher the temperature, the faster the speed of movement with all the species of mites. 8. H. rostrolamellatus was more active in moist air than in dry air; B. geniculosa was more active in dry air than in moist; results with F. fuscipes were variable. 9. The activity of individual B. geniculosa in a humidity gradient differed from the activity of batches of mites under the same conditions. Contact stimuli accounts for this difference in behaviour. 10. The orientation mechanism and behaviour of single B. geniculosa at humidity boundaries are discussed. 11. The humidity receptors are probably located on the forelegs.
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