February, '19] PIERCE: ENTOMOLOGY AND DISEASE 43 



order that we may more quickly solve the many problems ahead 

 of us. 



In the study of disease transmission we must work directly with 

 doctors, and parasitologists in perfect harmony. It is our role to 

 understand the life-histories of the insects, their hosts and their para- 

 sites, in order that we may point out the possible manners of transmis- 

 sion, to assist in the transmission experiments, and to maintain the 

 surroundings of the experimental insects such that the experiments can 

 be successfully concluded. The doctor and the parasitologist will be 

 just as concerned with the patient and the organism as we are with the 

 carrier. Had such cooperation been in effect in the past, it would not 

 be now necessary to reconduct many transmission experiments which 

 proved failures because of faulty technique in handling the insects, or 

 efforts to obtain transmission by bite when it should have been accom- 

 plished by some other method. 



Briefly, we must summarize the methods of disease transmission by 

 insects. The organism may be carried mechanically on the body or in 

 the mouth parts, or maj^ pass through the body of the insect and out 

 with its feces. The host may be infected by the insect coming in con- 

 tact with food or wounds, or by mechanical inoculation at the time of a 

 bite, or by the insect being scratched into a wound, or by having its 

 feces scratched in. Its feces may be dropped on food or be washed 

 into the blood by fluids excreted by the insect at the time of feeding. 

 The organism may require the insect as an intermediate host, and may 

 follow many devious paths in the insect body, emerging from the 

 region of the mouth or anus, or may never be contaminative in this 

 manner, but require to be swallowed in its insect host by the next host 

 in its cycle. Insects httle suspected of having any role in disease 

 transmission are often vital elements in the economy of a disease 

 organism. 



Since the beginning of the war the body-louse has assumed a primary 

 importance as a carrier of some of the most dreaded diseases. Val- 

 uable studies have been made in India on the role of the bedbug as an 

 intermediate host of Kala azar and kindred diseases. Further ad- 

 vances have been made in the study of sleeping sickness in Africa. 



An outstanding feature of the louse and bedbug studies is the fact 

 that these insects do not spread diseases by biting, but by being 

 scratched into the flesh or having their feces scratched in. The impor- 

 tance of these studies must not be minimized, for quite possibly we have 

 here a probable explanation of the means of ingress for a ninul)er of 

 other diseases which have baffled investigators. 



The part of insects in materia medica is but little knowii and is a 

 field for future investigations. Certain it is, however, that insect 



