310 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 5 



toward eliminating as many species of insects as possible, and at the 

 same time ascertaining if any might seem of sufficient importance to 

 warrant more detailed field work and experimental tests in- the lab- 

 oratory. In entering upon such an investigation one is naturally led 

 to pass in review such insects or groups of insects as have been proved 

 to be factors in the transmission of other diseases. So far as our 

 present definite knowledge extends, the accompanying tabulation is 

 submitted. (See Table 1.) 



From Table 1 it will be seen that the following groups of insects 

 have been implicated in the transmission of diseases among man and 

 domestic animals, including also ticks, which are, of course, not true 

 insects, but, owing to their similar habits and other characteristics, 

 are usually dealt with by entomologists: Acarina, Hemiptera, Coleop- 

 tera; Diptera, Siphonaptera. 



Of these, only the Acarina (ticks), Hemiptera (true bugs) and 

 Diptera (mosquitoes, flies) are known to include specific carrie-s, that 

 is to say, insects upon which the pathogenic organisms are parasitic, 

 and the presence of which is necessary for the organisms to complete 

 their life cycle before they can again normally reenter their mammalian 

 hosts. The members of the other groups, as well as a numl^er of those 

 belonging to the Diptera, are known to transmit some diseases casually 

 or accidentally, simply by cariying the bacteria upon their bodies, 

 feet or mouth-parts. Their relation is simply that of moving objects 

 to which the bacteria may adhere, but they are nevertheless very 

 commonly mechanical carriers for certain diseases, the organisms of 

 which occur often in materials that they frequent. Most important 

 among these is the common housefly, which is eminently suited to 

 play a part in such transmission as it regularly feeds upon both food 

 and fecal matter. 



While it cannot be so stated definitely, it seems probable that practi- 

 cally all insect-borne chseases will be found to depend for their spread 

 upon insects belonging to the groups enumerated in Table 1. These 

 various groups exhibit much in common in their mode of life and 

 a comparison of such facts, with what has been learned concerning 

 the spread of anterior poliomyelitis, serves to eliminate many insects 

 which by reason of their mode of- life cannot be suspected as carriers. 

 Still following the assumption that the disease is insect-borne it is 

 thus possible to curtail greatly the list of insects which would seem to 

 require investigation. 



Among the Hemiptera, the groups so far shown to contain species 

 acting as disease carriers, all include either wingless insects (lice, 

 bedbugs, etc.), or else large bugs of rather rare occurrence in our 

 region, which are characterized bj^ such painful bites (Reduviid bugs. 



