32 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 6 



typhoid fever, tuberculosis, leprosy, poliomyelitis, dysentery and other 

 diseases in which insects are known to be concerned. In the case of 

 diseases of domestic animals we have splenetic fever of cattle, and there 

 is a strong suspicion that infectious anemia of horses is transmitted by 

 Stomoxys calcitrans, to say nothing of the possible presence within 

 our boundary also of spirillosis of fowls transmitted in other countries 

 by a tick which is very common in the Southwest. 



In the group of exotic diseases of man we have yellow fever, plague, 

 cholera and others. Our public health service is wide awake and 

 efficient, but the impossiblity of preventing the invasion of our country 

 by exotic diseases is shown by the presence of plague in California and 

 the outbreak of yellow fever in New Orleans not later than 1905. As 

 long as it seems to be humanly impossible to prevent the invasion of 

 such diseases, the study of the native insects which can transmit them 

 will require investigation. 



The danger of the introduction of new diseases in this country is 

 illustrated in a case of shipment of Indian cattle which was brought to 

 New York a few years ago. In order to be safeguarded, a veteri- 

 narian accompanied the importer to India where he made repeated 

 blood examinations of every animal that was selected. Such care is 

 not exercised with human immigrants. The examinations were con- 

 tinued while the cattle were en route. As an extra precaution the 

 animals were kept at quarantine off the harbor at New York for some 

 weeks. Here it was found that the trypanosome which is the causative 

 agent in surra was present. It is not difficult to imagine similar cases 

 in which diseases might pass through the quarantine. In the case of 

 surra, for instance, we have a number of species of insects that can 

 carry it from one aninal to another. In fact, we have one of the 

 identical species, Stomoxys calcitrans, which has been proven to be a 

 transmitter of this malady in the Philippines and elsewhere. 



Narrowing our inquiry we will now consider the four specific diseases 

 of man and one of cattle occurring in the United States, which, as 

 far as known, are transmitted only by- insects. These are malaria, 

 dengue, spotted fever, typhus, and splenetic fever of cattle. 



Ver}^ recently students of conservation have furnished data that 

 lead to much greater exactness in the determination of the losses 

 caused bj^ human diseases than was formerly possible. The most 

 notable work of this kind has been done by Prof. I. Fisher of Yale 

 University. As the result of most careful calculations he has concluded 

 that the average economic value of the lives now sacrificed by pre- 

 ventable diseases is $1,700. He has also estimated in certain cases 

 the loss due to invalidism not resulting in death. These determina- 



