NORTH AMERICAN DIPTERA. 



introduction from Europe, the first known American 

 specimens having been noticed in eastern Pennsylvania 

 in the spring of 1887; it has now extended over nearly 

 all of North America. An allied species is indigenous to 

 North America, living among the moose of the northern 

 woods. The tsetse flies* are perhaps the most famous of 

 the group. The diseases produced by the microparasites 

 (trypanosomes) transferred into their victims by their 

 elongated piercing proboscis are so dire in their results 

 that the regions certain species inhabit are rendered al- 

 most uninhabitable by the domestic animals. The dis- 

 eases also afflict certain wild animals, though with less 

 fatal results. The microparasites are, themselves, ap- 

 parently not regenerated in the flies, as is the case with 

 the mosquitoes, but are transferred by them shortly after 

 biting diseased animals to healthy ones. The fatal 

 'sleeping sickness' (trypanosomiasis) in man is occasion- 

 ed in the same way by the bites of Glossina palpalis. The 

 larvae of Glossina are born when well developed and ready, 

 or about to be ready, to become pupae, resembling those 

 of the Hippoboscidae in this respect. 



The limits of the Muscidae, both from the Sarcopha- 

 gidae and the Anthomyidae, are quite elusive and uncer- 

 tain; indeed they seem almost impossible of definition 

 save by the aid of artificial and trivial characters. 

 Girschner, and some other authors following him, would 

 unite the Calliphorinae, that is those with hypopleural 

 bristles, with the Sarcophagidae or Tachinidae. The log- 

 ical sequence would be to unite the Muscinae with the 

 Anthomyidae, abandoning the family. His views, how- 

 ever, have not been generally adopted. One genus with 

 bare arista has been generally united with the family, so 

 that the ultimate distinction from the Tachinidae would 



* An amateur dipterist has recently proposed in all seriousness to 

 separate the tsetse flies into an independent family, the Glossinidse ! 



