Figure 1. Insect Malpighian tubules (A), Malpighi’s original drawing of the MpTs (and gut) of the silkmoth Bombyx mori (Malpighi, 1669). The MpTs are indicated with arrowheads. (B) Schematic representation of the MpTs of Drosophila. Drosophila, has four MpTs, a longer anterior pair and a shorter posterior pair (a single anterior tubule is depicted). Each tubule is divided into four regions based on differences in cell structure and physiology along the proximodistal axis: initial, transitional, main segment and ureter. Two main physiologically distinctive cell types are known, principal cells (yellow) and stellate/bar cells (green). Midgut (MG) and hindgut (HG) are indicated. Image in A reproduced courtesy of the Royal Society of London.