32. On the Massing of the Ladybird, Hippodamia convergens (Coleoptera), in the Yosemite Valley

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Summary.

  • 1Crude experiments in the Yosemite Valley show that Hippodamia convergens responds by movement to both light and heat stimuli, whether separate, or combined. The optimum for each has yet to be determined.
  • 2The capacity to respond depends upon the length of time since hibernation began. A seasonal physiological insensitiveness to stimuli may be of considerable survival value.
  • 3Hippodamia convergens ate raisins, which they appeared to find by chance, and some continued to eat even when the low temperature had driven most to shelter.
  • 4Hippodamia convergens may be found hibernating in large masses at a variety of altitudes, but what determines that altitude is not yet known, or whether ladybirds which have grown in an altitude of, for example, 1000 feet would be physiologically capable of hibernating at an altitude of 7000 feet.
  • 5When biological forces have collected ladybirds in large numbers, then only, air-currents may have considerable effect upon their distribution and the positions where they ultimately hibernate.
  • 6Air-currents of great velocity might destroy ladybirds.
  • 7The effect of change of buoyancy upon ladybirds has yet to be determined.

Ancillary