Canadian Forest Service Publications
A model of foregut activity in the blowfly Phormia regina Meigen. III. Analysis of crop-valve function during the crop-emptying process. 1976. Thomson, A.J.; Holling, C.S. Canadian Journal of Zoology 54(7): 1140-1142.
Issued by: Pacific Forestry Centre
Catalog ID: 1625
Available from the Journal's Web site. †
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The crop valve (valve V4) in the blowfly foregut consists of circular muscles surrounding the opening of the crop duct within the crop. Although these muscles are anatomically part of the crop, which acts as a muscular pump, they act in a manner that imparts a valvular function to the structure. This variation in function is shown to be the result of differences between crop and valve in size and spacing of muscle fibres.