Our knowledge of the range of intermediate hosts of which Syngamus trachea can take advantage is increasing. Recent observations have shown that the centipede, Scolopendra sp., the leatherjacket, Tipula sp., and the spring tail, Sminthurus viridis may all act as vectors. In each case the larvae had migrated from the gut into the surrounding tissues where they had settled down. All these Arthropods have been found naturally infected on a plot of land known to be carrying a heavy burden of gapes.