STEPS TO PROVE INSECT CAUSATION OF DISEASE 31 



1. What insects coincide in distribution with the general distribution 

 of the disease? 



2. What insects occur in peculiar habitats of the disease? 



3. What bloodsucking insects occur in the locality under investi- 

 gation ? 



4. What is the relative abundance of these insects? 



5. Is there a coincidence between the season of abundance of any 

 of these insects and of the disease? 



6. What insects occur in the homes, nests, or haunts of infected 

 hosts? 



7. What insects are found on infected hosts? 



8. What insects occur in the working quarters of the patients ? 



9. What insects would be most apt to affect the particular group 

 of hosts most susceptible? 



10. What insects breed in or frequent the excreta of the hosts? 



11. What insects are found at the food of the hosts? 



12. What insects are found at the sources of the food of the hosts, 

 such as the milk? 



Vni. WHAT IS NECESSARY IN THE TRANSMISSION EXPERIMENTS? 



The investigations which have preceded will have narrowed the ques- 

 tion doAvn to certain species or groups of insects which need to be 

 critically studied. All of those insects which come in contact with the 

 blood or mucous membranes of the patient, or the food of the patient, 

 or the feces of the patient, must be given special attention. At this 

 point the bacteriologist, protozoologist, or the lielminthologist finds his 

 special work beginning. There will be many points which must be worked 

 out by cooperation of the parasitologist and entomologist. 



Considering first the bloodsucking insects, it is necessary to deter- 

 mine: 



1. Can. the particular insect take up the organism with the blood? 



2. Does the organism pass into the intestinal canal or does it stop 

 at some point en route? 



3. To what extent is the organism digested by the insect? 



4. In what organs of the insect can the parasite be demonstrated 

 from day to day? 



5. Are any changes in the organism demonstrable? 



6. What path does the organism seem to follow in the insect's body 

 from day to day? 



7. Does this movement of the organism suggest whether the trans- 

 mission is by inoculation or does it suggest that the organism will pass 

 out of the body in some of tlic excreta? 



