Dysdercus koenigi has two pairs of Malpighian tubules, each pair arising from a vesicle and forming a closed loop. The vesicles are connected dorsally, and the tubules are differentiated into proximal and distal regions with refractive granules in the latter and brush border in both.
In winters at Allahabad the embryonic period lasts about a fortnight, and on the 9th day, 4 small buds arise apparently from the anterior end of the proctodaeum. These grow rapidly and become tubular; their tips fuse, but the lumina remain separate. At this stage the met-enteric membrane (Henson, 1946a) stretches over the anterior end of the proctodaeum and an interstitial ring is differentiated, so that the zone of the origin of the tubules lies anteriorly to it and posteriorly to the met-enteric membrane. Meanwhile the basal part of each tubule swells and the two swellings of each side fuse, thus forming a vesicle on each side. A dorsal outgrowth from each vesicle meets its fellow of the opposite side. The tubules continue to elongate, at the same time becoming narrower, and ultimately only 3 cells can be seen in a cross-section. The tubules grow in 3 phases--(1) active mitosis, (2) of cell multiplication and cell rearrangement, and (3) of cell rearrangement and cell enlargement. Finally, the tips of each pair fuse completely and their lumina become continuous.
In the newly hatched first nymph the tubules are uniform throughout, but in the later part of this stage they become differentiated into proximal and distal regions and the striated or brush borders appear. Thus the embryonic development continues for some time in the first nymph. Once this condition has been reached, cyclical changes involving increase in the diameter of the tubules, in the size of the nuclei, and in the number of cells in the proximal region occur in each nymphal stage, but before each ecdysis the diameter decreases slightly. Thus the adult condition is reached in 5 distinct steps, corresponding to the 5 instars.
Henson's view that Malpighian tubules are endodermal is considered plausible, but his view regarding the primitive number of tubules is not accepted.