STEPS TO PROVE INSECT CAUSATION OF DISEASE 27 



IV. HOW SHALL WE RECORD OUR OBSERVATIONS? 



Undoubtedly the most satisfactory method of making a large series 

 of records is to use some type of loose-leaf card or sheet filing system. 

 By such means one can always keep in an orderly arrangement all the 

 facts so far obtained. In the case of investigations of the causation of 

 a given disease, one of the most satisfactory methods which has been 

 used for recording observations is to prepare a little blank booklet, which 

 will fit the filing system, in large quantities, each book to represent a 

 case. This book should contain pages for each phase of the question, 

 with blanks covering all kinds of minutias about this phase. The whole 

 series of observations can be tabulated for each point. 



V. HOW CAN AN INSECT BE INVOLVED IN DISEASE TRANSMISSION.'' 



Insects may be involved in disease transmission either by the trans- 

 mission of an organism or the inoculation of a toxin, or they may be an 

 intermediate host in the life cycle of an organism, but not come directly 

 in contact with the final host. 



1. What Kind of Organisms Can Insects Carry? 



It has been demonstrated that insects can carry bacteria, fungi, many 

 types of protozoa, and many species of parasitic worms, and also that 

 certain species of insects may be instrumental in carrying eggs of other 

 species of insects which cause disease. 



2. In What Manner May Insect Toxins Bring About Disease? 



Many species of insects which bite inoculate at the time of the bite a 

 toxin which may at times cause serious trouble. 



Some invertebrates inoculate the toxin by means of the mouth, some 

 by means of a claw, some by means of a caudal appendage, others by 

 means of the ovipositor. In some cases the invertebrate penetrates the 

 skin with its mouth parts and as long as it is adhering, toxins are created 

 which may in certain cases cause severe paralysis or death. The acci- 

 dental eating of certain insects in food will cause poisoning because of 

 the toxins contained in the bodies of the insects. It is believed, but not 

 yet satisfactorily demonstrated, that the pollution of food by the excreta 

 of certain insects may cause certain nutritional diseases. 



The presence of certain insects in the tissues causes severe irritations 

 and often the formation of toxins. 



