Calcium Storage in Face Fly (Diptera: Muscidae) Larvae for Puparium Formation1

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Abstract
The Malpighian tubules are shown to be the main storage site for Ca and other elements for puparium formation by the face fly, Musca autumnalis De Geer. Calcium in the anterior Malpighian tubules is stored in the form of amorphous, layered spheres 0.4 μm to >10.0 μm in diameter. Major elements in the composition of these spheres were Ca, P, and Mg, with traces of K. The weight of the tubules' content increased during the prepupal period. A major decrease then occurred and continued through the pupal period. The decrease results from movement of mineralized elements from the spheres and corresponds with the first significant amount of Ca and P found in the cuticle of the puparium. Mineralized spheres undergo dissolution in the proximal portion of the anterior Malpighian tubules, as indicated by external shrinkage and dissolution of internal layers, probably by changes in pH or enzymatic action.