DEFECATION BY THE MOSQUITO, AEDES-AEGYPTI, IS CONTROLLED BY THE TERMINAL ABDOMINAL-GANGLION

When the terminal abdominal ganglion (TAG) of female Aedes aegypti was surgically removed and the mosquitoes blood-fed on a rat, after 2 day s neither uric acid nor hematin were excreted and water loss was signi ficantly reduced. Urate was removed from hemolymph and accumulated in the midgut. TAG removal also prevented the elimination of a dye dissol ved in sugar. Similar results were obtained with mosquitoes in which d efecation was mechanically prevented by sealing the anus. Decapitation or transection of the ventral nerve cord anterior to the second abdom inal ganglion did not inhibit defecation, Egg development was not affe cted by TAG removal. Reimplantation of a denervated TAG partially rest ored uric acid and water excretion. These results suggest that the TAG specifically controls defecation, in part humorally, but it does not appear to interfere with the function of the Malpighian tubules.