XXXli. '21 | ENTOM()T.()(;iCAI. NK\VS 303 



Observations on Certain Siphonaptera.* 



Ctenocephalus canis Curtis; Ctenocephalus felis Bouche and Cerato- 



phyllus fasciatus Bosc. 



By E. M. CRAIGHEAD, Bureau of Plant Industry, Harrisburg. 



Penna. 



In January, 1917, experiments were started for the purpose 

 of confirming the theory that the flea may be a possible carrier 

 of Infantile Paralysis, as outlined by Dr. Mark W. Richardson 

 (1 and 2). 



Daily visits were made to an animal hospital and hundreds 

 of flea eggs were collected from mats where the dogs and cats 

 were confined. After several days' examination the author's 

 attention was called to the fact that not a single living larva 

 could be found; though many of the eggs had hatched. The 

 larvae died shortly after they emerged from the eggs. The 

 temperature of the room was 70 degrees F. or more, without 

 anv moisture, for doors and windows were always closed. This 

 very condition pointed out the fact that proper moisture 

 must be present for the survival of the larvae, and as a result 

 much time was saved in the laboratory experiments. This 

 same room, during the months of June and July, was without 

 heat ; windows and doors were open constantly and many larvae 

 completed their life history under these conditions. The former 

 conditions exist in many of our homes during the winter, thus 

 there is a decided decrease in the number of fleas. 



I'.ggs when laid upon a blanket were very easily removed, 

 but when laid in a test tube or any earthen ware they adhere- 

 to the container and require great care in removal. They were 

 placed in a small petri di>h. the bottom of which was covered 

 with blotting paper, and each day was slightly moistened with 

 water. The blotter retained sufficient moisture for the cage 

 and enabled the larvae to free themselves from the egg shells. 



Temperature and moisture have some effect on the time of 

 hatching of the eggs and the following table shows results 



* The observations and records that appear in this article are the re- 

 sults of Research Work carried mi at Harvard Medical School, and the 

 Massachusetts General Hospital, Boston, Massachusetts, during the 

 years 1917 and 1919. 



