ENTOMOLOGY

STEPS TO PROVE lNSECT CAUSATION OF DISEASE 311. What insects coincide in distribution with the general distributionof the disease?'!. What insects occur in peculiar habitats of the disease?8. What bloodsucking insects occur in the locality under investigation?4. What is the relative abundance of these insects?5. Is there a coincidence between the Beason of abundance of anyof these insects. and of the disease?6. What insects occur in the homes, nests, or haunts of infectedhosts?7. What insects are found on infected hosts?8. What insects occur in the working quarters of the patients?9. WiIat insects would be most apt to affect the particular ,groupof hosts most susceptible?10. What insects breed in or frequent the excreta of the hosts?11. What insecta are found at the food of the hosts?U. What insects are found at the sources of the food of the hosts,such as the milk?vm. WHAT IS NECESSARY IN THE TRANSMISSION EXPERIMENTS?The investigations which have preceded will have narrowed the questiondown to certain species or groups of insects which need to becritically studied. All of those insects which come in contact with theblood or mucous membranes of the patient, or the food of the patient,or the feces of the patient, must be given special attention. At thispoint the bacteriologist, protozoologist, or the helminthologist finds hisspecial work beginning. There will be many points which must be workedout by cooperatiQn of the parasitologist and entomologist.Considering first the bloodsucking insects, it is necessary to determine:1. Can the particular insect take up the organism with the blood?!. Does the organism pass into the intestinal canal or does it stopat 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 demonstratedfrom day to day?5. Are any changes in the organism demonstrable?6. What path does the organism seem to follow in the insect's bodyfrom day to day?'7. Does this movement of the organism suggest whether the transmissionis by inoculation or does it suggest that the organism will passout of the body in some of the excreta?