Graham-Smith (1913) states that although the stable-fly frequents stable manure, it is probably not an important agent in distributing the organisms of intestinal diseases. Bishopp makes the important observation that "it has never been found breeding in human excrement and does not frequent malodorous places, which are so attractive to the house-fly. Hence it is much less likely to carry typhoid and other germs which may be found in such places." Questions of the possible agency of _Stomoxys calcitrans_ in the transmission of infantile paralysis and of pellagra, we shall consider later. OTHER ARTHROPODS WHICH MAY SERVE AS SIMPLE CARRIERS OF PATHOGENIC ORGANISMS--It should be again emphasized that any insect which has access to, and comes in contact with, pathogenic organisms and then passes to the food, or drink, or the body of man, may serve as a simple carrier of disease. In addition to the more obvious illustrations, an interesting one is the previously cited case of the transfer of _Dermatobia cyaniventris_ by a mosquito (fig. 81-84). Darling (1913) has shown that in the tropics, the omnipresent ants may be important factors in the spread of disease. CHAPTER VI ARTHROPODS AS DIRECT INOCULATORS OF DISEASE GERMS We have seen that any insect which, like the house-fly, has access to disease germs and then comes into contact with the food or drink of man, may serve to disseminate disease. Moreover, it has been clearly established that a contaminated insect, alighting upon wounded or abraded surfaces, may infect them. These are instances of mere accidental, mechanical transfer of pathogenic organisms. Closely related are the instances of direct inoculation of disease germs by insects and other arthropods. In this type, a blood-sucking species not only takes up the germs but, passing to a healthy individual, it inserts its contaminated mouth-parts and thus directly inoculates its victim. In other words, the disease is transferred just as blood poisoning may be induced by the prick of a contaminated needle, or as the laboratory worker may inoculate an experimental animal. Formerly, it was supposed that this method of the transfer of disease by arthropods was a very common one and many instances are cited in the earlier literature of the subject. It is, however, difficult to draw a sharp line between such cases and those in which, on the one hand, the arthropod serves as a mere passive carrier or, on the other hand, serves as an essential host of the pathogenic organism. More critical study of the subject has led to the belief that the importance of the rôle of arthropods as direct inoculators has been much overestimated.