460 



L. K. CI.KVK1 VXD. 



the protozoa were not killed at all. It is evident, then, that mere 

 mechanical pressure does not kill the protozoa. 



2. Cockroaches. 



Since the protozoa of termites were so easily removed by oxy- 

 genation, it immediately became desirable to try the method on 

 other protozoa-harboring insects. The cockroach has many pro- 

 tozoa and can be obtained easily in quantity. By pressing on the 

 abdomen with the ringers or some mechanical instrument and 

 forcing out some of the intestinal contents it is not difficult to 

 determine just what protozoa an individual harbors, and the pro- 

 cedure does not injure the insect. Cockroaches with two ciliates, 

 Nyctotherus and Balantidium, and two flagellates, Lophomonas 

 and Polymastix, were oxygenated at 3.5 atmospheres. About 200 

 insects were used in these experiments. The minimum time re- 

 quired to kill all individuals of each of the four protozoan genera 

 is given in Table II. It is interesting to note that the flagellates 

 were both killed in 40 minutes, the same time required to kill the 

 flagellates of the large Pacific Coast termite (Termopsis*), at this 

 pressure, while the ciliates were not all killed until 3! hours, more 

 than five times the time required to kill the flagellates living under 

 identical conditions. From this it would appear that oxygen is 

 actually more toxic for flagellate protozoa. 



TABLE II. 



TIME REQUIRED AT 3.5 ATMOSPHERES OF OXYGEN TO KILL ALL INDIVIDUALS 

 OF CERTAIN INTESTINAL PROTOZOA OF 



Two other protozoa, an unidentified flagellate and Endamccba 

 blattcB, were present in some of the cockroaches, but not in a 

 sufficient number to make it feasible to work out the minimum 

 time required to kill them. They were killed. 



