Left hand image taken 23 seconds after the right hand one.
Feeding action is precisely controlled to maximize use of a food source with mimimum effort or waste. On a piece of glass coated with dried flour paste the foot was attached firmly to hold the shell stationary; the marks in the flour at 1 are at the same position relative to the shell in both images.
The head was extended and made a stroke of the radula to rasp flour to the stationary jaw and into the mouth (see 23Ch 23 Cepaea hortensis. Pennine foothills, V.C. Derbyshire, England. August 2018. ). The head was then moved slightly to the side and a second radula stroke made parallel and immediately adjacent to the first so it did not scrape any of the surface already dealt with, but left no waste between strokes except for a small triangle left by the narrowed tip (2). This was repeated until the head could swing no further (3).The timed swing of the head accommodated 15 radula strokes (8 marks visible, 7 estimated under the head) and took 23 seconds so each stroke and repositioning took c.1.5 seconds.
39 Cepaea hortensis feeding on dried flour paste on glass. Pennine foothills, V.C. Derbyshire, England. August 2018.
