INTRODUCTION. 



The Tabanidge are a group of blood-sucking insects which, though 

 of less importance to medicine than mosquitoes and certain groups of 

 flies, are nevertheless of sufficient interest to the student of animal 

 pathology to warrant a closer study and a completion of our meager 

 knowledge of the life history of these insects. As the group consists 

 of many species spread over all parts of the world, it is natural that 

 the work done hitherto has scarcely advanced beyond the systematic 

 and descriptive stage ; and the lack of information on development and 

 early stages is especially felt by experimental science. In fact, al- 

 though Tabanidae play a considerable part in transmitting diseases 

 of domesticated animals, and in spite of the trouble which their 

 presence in large numbers causes to horses and cattle even under 

 normal conditions, our knowledge of their life history is very incom- 

 plete compared with that which we possess of other groups of blood- 

 sucking insects; for instance, CulicidcT. Only recently the study 

 of tabanid life histories has been undertaken from the point of view 

 of their economic importance, by King, British Government Ento- 

 mologist in the Anglo-Egyptian Sudan, Mitzmain in the Philippine 

 Islands, and others. However, these authors practically ignore 

 previous or contemporary literature on the subject of their investiga- 

 tion. Thus Mitzmain states that the literature on the subject is 

 meager and quotes only three publications. When rediscovering 

 Graber's organ in the larvse studied by him, he assumes that the organ 

 is peculiar to this species or has been overlooked by the previous 

 authors. The Zurich Index (Concilium Bibliographicum), however, 

 contains reference to several publications of European authors on 

 this organ. 



I have undertaken a review of the literature on the subject because 

 the entomological literature is especially difficult of access, being 

 scattered over a number of small periodicals appearing in different 

 languages. Field and experimental work on entomological subjects 

 is often done at a great distance from large libraries, and it would be 

 an advantage to the individual worker, especially in the tropics, to 



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