772 Charles Paul Alexander 



of the species here included. Present knowledge of the biology and ecology 

 of these species, and exact data on the duration of the different periods 

 of the immature stages, arc still very meager, and it is this field more than 

 any other that offers the greatest opportunities for research. 



The classification herein adopted is that of Osten Sacken, but it may 

 be well to state that very many fundamental changes are to be expected 

 when the immature stages are better known. 



In the course of the author's studies on the local Tipulidae, it was 

 necessary for him to visit and examine most of the important collections 

 in the East. In some cases in which it was impracticable to visit the 

 museums, specimens were lent by the authorities in charge. The writer 

 wishes to express his gratitude to the persons who kindly assisted in this 

 manner. Among the collections studied were those contained in the 

 following institutions: 



United States National Museum, Washington, D. C. This museum contains probably 

 the largest collection of crane-flies in the New World, including the types of Coquillett and 

 the Limnobiinae described by Doane, as well as much of the material determined by the 

 author. The collection was examined on several occasions thru the kindness of the late 

 Mr. Frederick Knab, custodian of the Diptera. 



United States Biological Survey, Washington, D. C. The collections here, examined 

 thru the kindness of Mr. W. L. McAtee, are extensive, and are particularly rich in local 

 forms and in material from the Pribilof Islands. 



Museum of Comparative Zoology, Cambridge, Massachusetts. These collections, examined 

 on several occasions thru the kindness of the Director, Mr. Samuel Henshaw, include the types 

 of Osten Sacken and Loew and are of the greatest importance on that account. The material 

 is in a fine state of preservation because of the constant care given to it. 



Boston Society of Natural History, Boston, Massachusetts. These collections, examined 

 thru the kindness of the Curator, Mr. Charles W. Johnson, are very fine, almost complete 

 as far as the New England fauna is concerned, and of great value to the student. The type 

 of Chionea valga Harris, as well as many of Say's species and the specimens determined 

 by him, are to be found here. 



Academy of Natural Sciences, Philadelphia, Pennsylvania. The material here includes 

 the collections of the American Entomological Society. The collections were examined 

 thru the kindness of Mr. E. T. Cresson, jr. They include the type of Triogma exculpta 

 Osten Sacken, and cotypes of many of the other Sackenian species as well as a good repre- 

 sentation of other forms. 



American Museum of Natural History, New York City. This rather considerable col- 

 lection, examined thru the kindness of Dr. F. E. Lutz, includes many of Williston's cotypes 

 and is especially rich in Antillean and South American forms. 



Museum of the Brooklyn Institute, Brooklyn, New York. This collection was examined 

 thru the kindness of the custodian, Mr. Charles Shaeffer. It is a rather small local collection, 

 but the specimens have been authoritatively determined by Johnson and they form a good 

 nucleus for future work. 



