The principal reason for regarding this phase of the subject as relatively unimportant, is derived from a study of the habits of the blood-sucking species. It is found that, in general, they are intermittent feeders, visiting their hosts at intervals and then abstaining from feeding for a more or less extended period, while digesting their meal. In the meantime, most species of bacteria or of protozoan parasites with which they might have contaminated their mouth-parts, would have perished, through inability to withstand drying. In spite of this, it must be recognized that this method of transfer does occur and must be reckoned with in any consideration of the relations of insects to disease. We shall first cite some general illustrations and shall then discuss the rôle of fleas in the spreading of bubonic plague, an illustration which cannot be regarded as typical, since it involves more than mere passive carriage. SOME ILLUSTRATIONS OF DIRECT INOCULATION OF DISEASE GERMS BY ARTHROPODS In discussing poisonous arthropods, we have already emphasized that species which are of themselves innocuous to man, may occasionally introduce bacteria by their bite or sting and thus cause more or less severe secondary symptoms. That such cases should occur, is no more than is to be expected. The mouth-parts or the sting of the insect are not sterile and the chances of their carrying pyogenic organisms are always present. More strictly falling in the category of transmission of disease germs by direct inoculation are the instances where the insect, or related form, feeds upon a diseased animal and passes promptly to a healthy individual which it infects. Of such a nature are the following: Various species of biting flies are factors in the dissemination of anthrax, an infectious and usually fatal disease of animals and, occasionally, of man. That the bacteria with which the blood of diseased animals teem shortly before death might be transmitted by such insects has long been contended, but the evidence in support of the view has been unsatisfactory. Recently, Mitzmain (1914) has reported a series of experiments which show conclusively that the disease may be so conveyed by a horse-fly, _Tabanus striatus_, and by the stable-fly, _Stomoxys calcitrans_. Mitzmain's experiments were tried with an artificially infected guinea pig, which died of the disease upon the third day. The flies were applied two and one-half hours, to a few minutes, before the death of the animal. With both species the infection was successfully transferred to healthy guinea pigs by the direct method, in which the flies were interrupted while feeding on the sick animal. The evidence at hand does not warrant the conclusion that insect transmission is the rule in the case of this disease.